Speed Management Hub
Frequently Asked Questions
Speed management involves various techniques to reduce/modify the speed of road users, usually motorized vehicles. The purpose is to ensure that speeds are safe for all road users to avoid injuries and death, as well as to improve traffic flow, reduce noise and air pollution, and decrease climate change impacts of road transport.
The management of speed can be achieved through the use of appropriate speed limits, provision of road infrastructure to support these limits, police enforcement, education and community engagement, and vehicle technologies. A mixture of these approaches is often used and the most effective. Speed management should occur as part of a structured, consistent approach that covers the entire road network of interest. However, in many instances, localized changes to speed may be required, often in response to local safety issues.
Under the Safe System approach, safety is the key objective when managing speeds, with a requirement to set and encourage speeds that avoid death and serious injury for all road users, particularly the most vulnerable (including pedestrians and cyclists). Decisions on the appropriate speed often include reference to other societal outcomes besides safety mentioned above, including vehicle journey time, noise and emissions.
The Safe System approach is a human centric approach in the road transport system which highlights that deaths and serious injuries on our roads are unacceptable and avoidable, and this should dictate the design, use and operation of our road networks. The approach has been adopted by key global organizations (including the World Bank, WHO, United Nations, PIARC, and others) as well as those countries with the best road safety outcomes.
The approach highlights various key principles, including that:
→ People inevitably make mistakes that can lead to road crashes;
→ The human body has a limited physical ability to tolerate crash forces before serious harm occurs;
→ There is a responsibility on those who design, build, and manage roads and vehicles, as well as those who provide post-crash care to prevent crashes resulting in serious injury or death; and
→ All parts of the system must be strengthened to employ their effects so that if one part fails, road users are still protected.
Speed is a critical component within a Safe System. Safe speeds (see Q1.4) are needed to ensure when errors do occur, that they do not result in death or serious injury. The levels which speeds are considered safe depend upon the presence of vulnerable road users, vehicle types (and their protective features), and the protective nature of road and roadside infrastructure. Speeds at or below these levels will help eliminate death and serious injuries, which is the ultimate goal of the Safe System approach.
Learn more from the OECD/ITF Safe System guide here. To understand more about the origins of the Safe System approach, see a summary on Sustainable Safety from the Netherlands here, and on Vision Zero from Sweden here.
Speeding refers to road users travelling at speeds which are above the speed limit, also called as excessive speeds (which is dangerous and illegal), and also speeds that are inappropriate for road conditions (e.g. driving too fast during heavy rain or fog). Both of these have negative impacts on road safety outcomes and need to be addressed.
Sometimes a distinction is made between ‘high level’ or excessive speeding (often deliberate, and well above the speed limit) and ‘low level’ speeding (just above the speed limit, and sometimes unintentional). Both have an impact on safety outcomes (see Q8.4 for a discussion on how even small changes in speed can have a big safety impact).
The UN Global Road Safety Performance Targets indicate in target 6 the need that “by 2030, halve the proportion of vehicles travelling over the posted speed limit and achieve a reduction in speed related injuries and fatalities”.
To be safe and appropriate, speeds need to reflect the type of road users that are likely to be part of the traffic mix, the protection offered by vehicles and road design, and be adapted to conditions, including weather.
When errors do occur (see Q1.2), the outcomes should not result in death or serious injury, and speed plays a critically important role in this. There are only certain forces that the human body can withstand during a crash, so speeds should be managed based on our understanding of this. Pedestrians can typically survive impacts speeds of around 30 kph, above which the chance of survival decreases dramatically. It is likely a similar impact speed applies for other unprotected road users such as motorcyclists and cyclists. At intersections, side impacts at or below 50 kph are survivable. For head-on crashes, road users in modern vehicles with good quality safety features can generally survive an impact at 70 kph with another vehicle of equal mass. To be safe, speeds need to be at or below these critical threshold levels.
If higher speeds are required, then better-quality infrastructure (including separation and crossing facilities for pedestrians; barrier protection systems to prevent head-on crashes etc.; see FAQs in section 3 for further examples) is usually required to support the increase in operating speed and protect road users.
Reaching safe speeds to eliminate death and serious injury should be the ultimate objective for road safety. However, where these speeds cannot be obtained in the short term, less substantial reductions in speed will also produce safety benefits (for information on this see Q1.9 and Q8.4).
Read more about Safe System speed limit setting here.
There are several reasons (excuses) why drivers speed. A recent study characterized motivations and types of speeders using naturalistic driving data (Richard et al., 2012 for a summary of findings; also see Richard et al., 2013).
Speeders were classified into four general patterns based on the percentage of trips with speeding and the average amount of speeding per trip. The four patterns were:
1. incidental or infrequent speeders meaning less trips with speeding and little speeding on thse trips;
2. situational speeders meaning less trips with speeding but a lot of speeding on these trips;
3. casual speeders meaning many trips with speeding but only small amounts of speeding ; and
4. habitual speeders meaning speeding on most trips with a lot of speeding.
Speeding is a type of aggressive driving behavior, but what makes drivers do it?
→ Traffic - Traffic congestion is one of the most frequently mentioned contributing factors to speeding. Drivers feel the need to “make up the time lost” during congestion.
→ Running Late - Some people speed because they have too much to do and are “running late” for work, school, their next meeting, lesson, soccer game, or other appointment.
→ Anonymity - A motor vehicle insulates the driver from the world. Shielded from the outside environment, a driver can develop a sense of detachment, as if an observer of their surroundings, rather than a participant. This can lead to some people feeling less constrained in their behavior when they cannot be seen by others and/or when it is unlikely that they will ever again see those who witness their behavior.
→ Disregard for Others and For the Law - Most motorists rarely speed, and some never do. In addition, many people speed occasionally. For others, episodes of speeding are frequent, and for a small proportion of motorists it is their usual driving behavior.
This study also found that young males and young females in urban settings and young males in rural settings are more likely than older drivers to speed. For more information see link here.
A 2020 survey by CarInsurance.com in the US reported that during the current COVID-19 pandemic many countries are reporting more traffic fatalities and handing out more speeding tickets. Fewer drivers on the road are leading motorists to take more risks, including speeding. About one-fifth of those surveyed explained they were late for work, didn’t see the sign, drove as fast as everyone else or had a medical emergency. Other excuses not quite as popular were they were headed for an interview, funeral, date and concert. For further information, see this link.
Additionally, the Transport Accident Commission in Victoria, Australia, in their Road Safety Monitor 2019, reported on drivers’ perceptions of speeds - see here.
About 650,000 people are estimated to die annually in road crashes because of speeding (for a definition of speeding see Q1.3), though this is most likely an under-estimate. Various studies indicate that speed is responsible for about 30%- to 50% of deaths on the road.
Although many studies indicate this level of contribution, many also qualify this to be an under-estimate, making speed an even higher proportion of road crashes. More significant is that reductions in speed can result in substantially greater levels of fatal and serious injury reduction (60%+).
The relationship between speeds and crash outcome has been captured in various models, most notably Nilsson’s “Power Model”. This shows that a 1% increase in average speed results in approximately a 2% increase in injury crash frequency, a 3% increase in severe crash frequency, and a 4% increase in fatal crash frequency (see Q1.7 to understand better the impact of speed). Thus, this model shows how decreasing speed by only a few km/h can significantly reduce the risks of and severity of crashes. Lower driving speeds also benefit quality of life, especially in urban areas as the reduction of speed mitigates air pollution, greenhouse gas emissions, fuel consumption and noise (see Q1.8 and Q1.9).
The higher the speed, the bigger and the more likely the mess. The operating speed of a vehicle impacts not only crash occurrence, but also the severity of a crash when it happens, through the driver’s field of vision and stopping distance (which covers the time to see and judge the need to stop – judgement time, moving to the brake and pressing it - reaction time, and actually stopping the vehicle - braking time), and also crash kinetic energy and losing vehicle control.
The faster a vehicle is moving, the more information the brain receives. However, the brain can only process a certain amount of information in any given time, which means that at 100 kph, it has to eliminate a large amount of peripheral information. This happens unconsciously. The field of vision therefore decreases as speed increases. See this gif showcasing how a driver’s peripheral vision at higher speeds.
In calculating the stopping distance, judgement and reaction time represent how long a driver takes to see both a hazard and the time it takes the brain to realize the danger and process a reaction to a hazard for example, starting to brake. This means that a vehicle travels further at higher speeds before they can react to a hazard. Although several studies have shown that a driver can react in as little as 1 second, most response times are between 1.5 and 4 seconds. The braking distance is the distance that a vehicle travels while slowing to a complete stop. As your speed increases - so does the distance you travel while your brain is processing information and reacting to it – and so does the distance you need to stop. So, the higher the speed, the higher the braking distance.
The kinetic energy of a moving vehicle is a function of its mass and velocity squared (E=1/2mv2) and this energy must be absorbed in a crash by friction, heat, and the damage suffered by the vehicle as a result of the crash. This means, the more kinetic energy to be absorbed in a crash, the greater the potential for injury to vehicle occupants and anyone hit by the vehicle.
Another way speed impacts road crashes and injury is by losing vehicle control: at higher speeds, cars become more difficult to maneuver - especially on corners or curves or where evasive action is necessary.
At the same time, higher speeds may also add risk for other road users. For example, a pedestrian may have selected a safe location to cross the road with sufficient site-distance to the crest of a hill or corner. However, a speeding driver may cover the distance from the position of not being visible to the crossing pedestrian much faster and thus hit the pedestrian.
The National Association of City Transport Officials (NACTO) presents the example below for an impactful communication of speed on fatalities from the city of Portland. Access the full document here.
Speed not only affects road safety but also several environmental and health outcomes, such as:
→ Level of traffic noise: Road noise is the collective sound energy originating from motor vehicles as a result of friction between tire and the road surface, and also from the engine/transmission, aerodynamics, and braking elements. The noise of rolling tires driving on the pavement is found to be the biggest contributor to highway noise which increases with higher vehicle speeds. There is a link between traffic noise and health, with increases in noise leading to negative health outcomes.
→ Air pollution through the level of exhaust emissions: Speed has important impacts on air pollution as it is strongly related to the emissions of greenhouse gases (mainly CO2) and of local pollutants (CO, NOx, HC, particulates). While the process of emission generation is complex and varies within vehicles, across vehicle classifications and engine technologies, oxides of nitrogen (NOx) are produced particularly at high engine operating temperatures (e.g., steady high-speed driving) and a reduction in speed leads to a significant reduction in these emissions. Learn more on speed and environment from OECD (2006).
→ Fuel consumption: Speed also affects fuel consumption with most cars' fuel efficiency reaching a peak at speeds from 60 to 80 kph (equivalent to 35 to 50 miles per hour), but varies for vehicle type. In urban environments with regular slowing and stopping, the most fuel-efficient peak speed may be much lower. Fuel consumption is also linked to air pollution and greenhouse gas emissions. In a high-speed environment, i.e., in non-congested conditions, fuel consumption and CO2 emissions increase with increasing speed. However, at lower speed levels, reduced speeds do not necessarily lead to reduced fuel consumption. At speeds below 20 kph, fuel consumption increases significantly as well as air pollution.
→ Overall quality of life for people living or working near the road: As high-speed increases risk of road traffic crashes and injuries, but also air and noise pollution, there is no doubt that speed is linked with poor health and decreased quality of life. Unfortunately, it is a myth that speed means prosperity and progress when in reality, only a marginal benefit can mathematically be derived from increased travel speeds. For example, the extra travel time required for a 10 km journey will be less than 2 minutes if the travel speed is reduced from 50 kph to 45 kph (see 8.7 or more details on this myth). In stop/start traffic (which is typical in urban areas due to congestion and intersections) the increase in journey time is likely to be far less.
For more information, check out this study from the OECD (2006).
Road safety outcomes are usually measured in terms of the number of crashes and their severity levels, e.g., the total number of crashes; the number of fatalities and serious injuries. Speed plays a central role in all of these road safety outcomes.
There have been several research studies to quantify safety outcomes from speed changes. Much of this research comes from comparing outcomes before and after changes are made. This research is best summarized through Nilsson’s “power model” which shows that a 1% increase in average speed results in approximately a 2% increase in injury crash frequency, a 3% increase in severe crash frequency, and a 4% increase in fatal crash frequency. More recent research by Rune Elvik suggests that the relationship between collision risk and speed is exponential, and not a power law. The practical implication of this finding is that the rate of increase in crash risk varies with the initial speed level such that the effect of speed change is higher for high-speed roads than for lower speed roads. Also see here for an update.
According to the WHO Global Status Report on Road Safety 2018, only 46 countries representing 3 billion people currently have laws setting speed limits that align with best practice. This number has not changed since 2014, and an interactive map with speed limits worldwide can be viewed here.
Globally, there are mainly three different types of speed limits:
1. Default speed limits as specified in relevant legislation (e.g. Road Code), which set the general maximum speed allowed on specific types of roads such as motorways or urban roads; no additional signposting is needed to enforce these limits.
2. Signposted maximum speed limits on roads or sections of roads.
3. Speed limits for specific vehicle or road user types – e.g. farm vehicles, heavy transport vehicles or novice drivers.
It needs to be noted that the default speed limit as well as the posted speed limit indicate the maximum allowable speed for a certain road or stretch of road and not the recommended or appropriate speed at a specific location.
It is also possible to set variable speed limits (VSL). These are flexible restrictions on a certain stretch of road. The speed limit changes according to the current road, traffic, weather or environmental conditions and is displayed on an (electronic) variable message sign (VMS) or on static signs. A VSL may also be used in school zones to provide a safer road environment, to reinforce driver expectations of the likely presence of children and to encourage safe and active travel to school.
Finally, there are also so-called differential speed limits (DSL) with different speed limits for different types of vehicles on the same type of road, e.g. for cars and trucks on motorways.
You want to know more? Click here.
Determining the ‘right’, compliant speed limit from a Safe System perspective (see Q1.2) for your road is a very complex task depending on the local factors at hand. Still, you might base your decisions for setting speed limits on the following four principles:
a. Road safety principle
→ Set speed limits to minimize the risk of death or serious injury to all road users where vehicle speeds would result in impact forces exceeding tolerance of the human body.
→ Set speed limits to minimize the risk of death or serious injury to all road users when there is an increased risk of crashes due to a change in operational and/or environmental conditions.
b. Community wellbeing principle
→ Set speed limits, especially on local roads, at a level that supports active transport modes (walking, cycling) and minimizes impacts on amenity.
→ Set speed limits by consulting the affected communities and road users so that expectations, where possible, are considered and impacts of speed changes are understood by the public.
c. Road network efficiency principle
→ Set speed limits in accordance with the functional road class and the standard of the infrastructure.
→ Set speed limits to achieve operating speeds that support an efficient network wide outcome and do not just focus on one isolated section of road.
→ Set speed limits to minimize the overall delay to road users where there is a change in operational conditions (e.g. by variable speed limits, see Q2.1).
d. Road user expectation principle
→ Set speed limits to be consistent with speed limits on roads in a similar environment with similar characteristics and function.
→ Set speed limits so they are clear and easily understood and keep the number of speed limit changes to a minimum.
Among these four, the road safety principle is the most important and should therefore be given priority whenever one principle has to be weighed against another in the decision-making process.
Policy on the minimum length of speed limits is also vital. Speed limits should not change regularly over a few hundred meters, for example. Too many limit changes create confusion and frustration for drivers. Thus, it may be appropriate to set a minimum length for each speed limit. For each section the posted speed limit should be determined as the lowest safe speed for any location within that length.
Spot speed measurements are your way forward. These measurements can be used to assess free flow speeds on a representative sample of urban and rural roads as an important basis for setting up a speed management strategy.
The spot speed is defined as the instantaneous speed of a vehicle at a certain point or a specified location. In road safety work spot speeds are for example used as basic input data for crash analysis, but are also required for road design (e.g., horizontal and vertical curves, super elevation) and to determine the location and size of signs and the design of signals.
There are different techniques to measure spot speeds. The most common devices use either radar (radar meters) or laser sensors (speed lasers), which may be hand-held (so-called ‘speed guns’), mounted in a vehicle or on a tripod. Radar and laser devices require line-of-sight to accurately measure speed and are easily operated by one person. If traffic is heavy or the sampling strategy is complex, two units may be needed.
Besides using radar or laser technology, spot speeds may be estimated manually by measuring the time it takes a vehicle to travel between two defined points on the road, which are a known short distance (e.g., 1 m) apart. This technique is often called stopwatch method. The measurements are very simple and can be conducted by either two observers or by using an enoscope (mirror box) and only one observer. Manual measurements are only applicable for very low traffic volumes and a small sample size taken over a relatively short period of time.
For longer data collection periods pressure contact tubes (pneumatic or electric) can be used. Two contact tubes are placed in the travel lanes of the road and the time is measured between the electric impulse generated when a vehicle runs over the first and then the second tube. The advantages of this method include the ability to collect and store data on 100% of vehicles, and capacity to continuously record for many hours and days. In addition, there is no risk of driver behavior being influenced by seeing a person ahead with a ‘speed gun.’
The most advanced (and expensive) technologies use traffic monitoring cameras and software algorithms to determine speeds from real-time traffic data. An ever-emerging research field is real-time traffic monitoring using mobile phone data or GPS data and estimating traffic speeds using these data sources. Due to the high market penetration of mobile phones not only in HICs but also in LMICs, very detailed spatial data at lower costs than with traditional data collection techniques would be available. Data from cellular phones open new and important developments in transportation engineering but several steps are still needed to achieve a significant confidence in the use of these data, not only in terms of data reliability but also regarding privacy and security issues.
Regardless of the speed measurement method used, you might keep in mind that speed survey results highly depend on the way the survey is conducted. Therefore, you might follow these steps:
1. Select appropriate location for the specific purpose of the study considering that the location is safe for the operator and away from specific features that might influence speeds.
2. Select appropriate speed measuring device (e.g., contact tubes) for the specific purpose of the study.
3. Choose sample size considering the different types of vehicles using the roads (motorcycles, cars, lorries), the traffic volume and variables such as time of day, day of week, holidays and weather conditions (e.g., 200 vehicles of each type over a minimum of 2 hours).
4. When measuring free flow speeds select those vehicles that have a substantial headway and are not impeded by other vehicles or other factors (minimum headway of 3-4 seconds is recommended). Note that for some purposes, collection of speeds from all vehicles (i.e., not including a minimum headway) may be desirable.
5. Guarantee minimum influence of the observer and/or equipment on the drivers and their speed (hide observer and recording equipment, if possible).
6. Collect and evaluate the data (minimum evaluation should include average speed and 85th percentile speed).
It is a good idea to repeat speed surveys on a regular basis to show trends in vehicle speeds and monitor impact of speed management on driver behavior. In that case keep in mind the following:
→ Conduct the speed surveys under similar conditions each time, as any variation in collection procedures may result in differences in the speeds recorded.
→ Use the same location as well as the same recording equipment, and preferably the same equipment operator.
You can learn more here from a New Zealand case study, or here from Austroad’s Transport Studies and Analysis Methods. A very useful document for you might also be the Overseas Road Note 11 ‘Urban Road Traffic Surveys’.
The free-flow speed is a drivers' desired speed on a road at low traffic volume and absence of traffic control devices. In other words, it is the average speed that a motorist would travel if there was no congestion or other adverse conditions (such as bad weather).
When measuring free flow speeds (see Q2.3) select those vehicles that have a substantial headway and are not impeded by other vehicles or other factors (minimum headway of 3-4 seconds is recommended).
Free flow speeds and 85th percentile speeds are NOT a good guide for selecting speed limits (see Q2.6).
The 85th percentile speed is the speed at which 85% of free-flowing vehicles (see Q2.5) are traveling at or below. For example, this speed can be determined by conducting and evaluating a spot speed study (see Q2.3).
The 85th percentile speed is often used by traffic engineers as the basis for road design. In many countries it is still used as primary tool for setting speed limits (Q2.2), and (more controversially) as a reason against lowering or enforcing limits. In this context, the following three misleading arguments for using 85th percentiles for setting speed limits are put forward:
2. The speed dispersion argument, i.e. speed limits near the 85th percentile will minimize the variance of the speed distribution, thereby minimizing opportunities for vehicle conflict and crashes.
3. The enforcement practicality argument, i.e. 85th percentile limits represent a reasonable and realistic benchmark for enforcement.
But none of these arguments are valid. The majority of drivers will not always make well-balanced decisions and select speeds that are safe. Speed choice will often be biased towards personal benefit (e.g. reduction in perceived travel times) as opposed to collective risk (e.g. overall crash risks). Also, drivers’ subjective assessments of risk, and the relationship between speed and risk, are likely to be inaccurate. As far as speed dispersion is concerned many studies showed that the majority of fatal crashes are crashes where speed dispersion is an unlikely factor (e.g. single vehicle crashes, intersection crashes, pedestrian crashes). Finally, nowadays there is strong evidence that setting and enforcing lower speed limits than the 85th percentile speed is feasible, sustainable, and produces safety benefits.
Therefore, countries that have already adopted the safe system approach have discontinued the use of 85th percentiles for speed limit setting. For these countries avoiding death and injury is an absolute priority, and the speed management system as a whole must be based on this philosophy and on an objective assessment of risks.
One short side note: The 85th percentile is an excellent way of demonstrating when speed limits and road design don’t match, and the design of a road is inappropriate for the posted speed limit. Here is an example:
On an inner-urban residential road the speed limit was lowered from 50 kph to 30 kph, without any changes to the road design for the motorized vehicles. The 85th percentile speed of motorized vehicles on this street is measured after the introduction of the lower limit and is found to be still close to 50 kph. This tells you that the road design isn’t doing its job. In the short term you could get the police out with speed guns, but in the long-term the design of the road and its environment should be changed by clever inner-urban road safety engineering solutions (see Question 3.2), which will reduce the 85th percentile speed.
Vulnerable road users such as pedestrians, cyclists or powered two-wheelers have a high risk of severe or fatal injury when they are hit by motor vehicles. This is because they are often physically completely unprotected or only have very limited protection, compared with the safety of a vehicle with a rigid safety shell and airbags.
The probability that a vulnerable road user will be killed if hit by a motor vehicle increases drastically with speed. If hit by a car at 30 kph, 10% of vulnerable road users die, another 15% are seriously injured and 75% are slightly injured. If the impact speed increases to 50 kph these numbers change dramatically: 80% die, 3% are seriously and 17% slightly injured.
The situation is even worse for elderly pedestrians. In fact, pedestrians over the age of 75 are twice as likely to be killed in a crash as those under 34. Elderly people are much more susceptible to injury if they are struck by a vehicle. Their bones are much frailer, and their overall state of health is worse – factors that can make even a minor crash turn lethal. Elderly pedestrians are also more vulnerable to being involved in a crash because of age-related declines in cognitive function and vision.
Children are also highly vulnerable to injuries from motor vehicle impacts. This vulnerability occurs for several reasons including that they have less developed cognitive and perceptual skills and so are less able to make decisions about safe behavior around traffic; the decisions they do make may be less predictable to other road users (such as running after a ball); they are smaller than adults, and so may be harder to see or be seen in traffic; and there is emerging evidence that they are more likely to suffer more severe injuries when struck as pedestrians (especially head injuries).
Under the Safe System approach (see Q1.2) the setting of speed limits considers the risks to road users of sustaining fatal or serious injuries. For example, at locations where there is a significant level of pedestrian or cyclist activity, lower speed limits are appropriate. Similarly, where the potential for conflicts is high (e.g., on busy urban roads with frequent points of access) speed limits are to be set at a level that will minimize the chances of fatal or serious injuries in the event of a crash.
Motorcyclists are becoming an ever more important component of the transport system. Increasing numbers of people not only in low- and middle-income but also in high-income countries are choosing to ride motorcycles.
This is potentially because of: a) the lower cost of purchasing motorcycles, b) increasing congestions, reduced parking availability, and increasing travel costs, and c) versatility and convenience of riding motorcycles. In some countries (especially high-income countries) there is also a growing interest in riding motorcycles among older and often returning riders, and this can be based on the reasons above, as well as interest in recreational riding.
The International Transport Forum (ITF) points out specific policies and strategies that directly influence a Safe System compliant choice of speed and motorcyclist speeding management policies, namely:
→ Conduct in-depth and naturalistic studies to better understand the role of speed and speeding in motorcyclist fatal and serious injuries.
→ Include motorcyclist safety and mobility in national transport policy including safety, green transport, livability, and sustainability.
→ Develop a policy of modal priority for road users, particularly in urban environments, based on vulnerability and sustainability goals.
→ Develop mandatory manufacturing rules and regulations to adopt motorcycle safety features such as motorcycle Anti-lock Braking System (ABS), Combined Braking Systems (CBS), stability control, and Automatic Emergency Call Systems. See also question 6.1.
→ Address the current difficulties in enforcing motorcyclist compliance with speed limits, and develop complementary education/enforcement policies and programs to address the motorcyclist excessive speed issue.
→ Develop enhanced enforcement programs with a focus on identified motorcyclist crash risk locations and popular motorcycling routes.
→ Consider zero-tolerance for motorcyclist speed enforcement or a minimal leeway.
Find the ITF reference here.
Road engineering activities range from minor improvements to small sections of existing roads, to major road works on regional or inter-regional developments. Road engineering addresses many facets of driving and road use such as human behavior, human expectations, visual cues, road features, lighting, signage, safety barriers etc. Road engineering design objectives include making road use as simple as possible for all road users, reducing the human error on that road, and therefore the likelihood of a crash. Effective design can also reduce the severity of the outcome should a crash occur.
Making the road function/usage and required speed clear through good design will reduce the likelihood of speeding, one of the main causes of road trauma.
For example, when a driver encounters not just lower speed limits but also road features such as well signalized and marked pedestrian crossings, roundabouts, traffic islands or gateway treatments, they become aware of a change in road environment, and more specifically of an increased number of vulnerable road users possibly sharing the same space, and are more likely to lower their speed through the area. Some additional design features that can help you control the road user behavior through engineering are road narrowing, speed platforms/humps or chicanes. A poor road design may not inform road users appropriately. This can lead to dangerous situations, including poor speed selection, last-minute decision-making, or sudden changes causing unpredictable behavior, leading to a higher likelihood of crashes.
Speed humps and other traffic calming must be visible to road users. This is especially important in higher-speed environments. For this reason, they must be implemented in conjunction with appropriate signage and linemarking. Advisory speed signs may be required based on the ‘safe and comfortable maximum speed.’
City areas are densely populated places where people live, meet, work, relax, or entertain. They are characterized by having particularly high numbers of vulnerable road users. The traffic flow is slow due to the high street activity and presence of pedestrians and other vulnerable road users such as cyclists and motorbikes. Furthermore, city areas include ‘special zones’ such as schools, hospitals, shopping streets, public transport hubs etc., where even higher concentrations of vulnerable road users are present.
This can include the elderly, people with disabilities, or equally important, children using the streets as an active playground. Creating an environment that is supportive and safe for children is safe for everyone. Read more about “Designing streets for kids” here.
In places with a large proportion of vulnerable road users and possible conflicts between pedestrians and cars, the speed limit should be no higher than 30 kph. When vulnerable road users are not present and safely separated from the vehicular traffic, and the risk of conflicts with vulnerable road users is low, the speed can be as high as 50 kph.
In these types of areas, traffic calming measures are necessary, such as:
Intersection traffic calming measures:
→ Roundabout or compact roundabouts: horizontal deflection
→ Raised intersections and crossing: vertical deflection
→ Horizontal deflection on approaches to intersection (to be considered at high risk locations)
→ Vehicle activated signs
Midblock traffic calming measures
→ Zebra and pedestrian signalized crossings (noting the effectiveness for each is highly dependent on good compliance by road users, and each crossing type needs to be installed in a suitable location).
→ Raised pedestrian crossing
→ Pedestrian refuges
→ Variable speed limits (VSL), for example, reduced speed limit during school drop off and pick-up time
→ Chicanes: horizontal deflection
→ Textured surfaces.
→ Speed cushion / hump / table: vertical deflection (used at high risk location)
→ Road narrowing (e.g., including through the use of sidewalks)
Learn more on the principles of improving urban road safety in Europe here. Learn more about engineering measures from NACTO here or here. See a Canadian guidance on traffic calming here, and an Australian guidance here. To see what London did to achieve lower speeds see here.
The roads in city outskirt areas are further away from a city or town centers and often in areas of high growth. In some cities, the outskirts are composed of business/commercial land with the population living in single dwellings rather than city multi-dwellings (apartments).
In many parts of the world, lack of planning and investment in infrastructure results in city extensions outpacing improvements in the road network. Travel is often on low-quality roads, with road quality improvements being slower than the increases in traffic, combined with less access to public transport.
This also includes roads leading out of cities where there is growing traffic, but poor provision for safety. There can be a mixture of road users, often because there are inadequate public transport networks. These factors reduce the ability to safely accommodate the traffic and protect its road users. The limitations of the public transport networks result in an increased number of vulnerable road users sharing the same road space as motorized traffic.
Speeds may be higher in these outskirt areas because they are often less developed (or were previously less developed) and they may also be regarded as semi-rural in nature. In such circumstances, maintaining high levels of safety becomes more difficult when travel speeds remain high and the road environment is unforgiving. Higher speeds are recommended only where high-quality infrastructure is provided and where vulnerable road users are not present.
The engineering measures shown below can be implemented when managing speed within city outskirts. Some of these solutions are better suited to high-risk locations (such as the speed cushion) whereas others can be used across the road network. In situations where there are high concentrations of vulnerable road users, some of the solutions more typically used in city centers, or in towns in villages should be used (see section 3.2 and 3.4).
→ Signalized intersection with dedicated pedestrian phase
→ Vehicle activated signs
→ Transverse rumble strips
→ Raised pedestrian crossings
→ Speed cushion / hump / table: vertical deflection (used at high-risk location)
→ Raised pedestrian crossings
→ Road diet (lane narrowing)
→ Reduced speed limit signs
→ Variable speed limits (VSL)
Towns and villages are clustered human settlements located away from city and city outskirt areas. While the definitions of 'town' and 'village' vary from country to country, generally a town is considered as an area larger than a village, often with improved infrastructure and availability of more services.
In comparison to a city, a town is generally smaller in size and population. Towns often do not provide all services and facilities (e.g., administrative services and commercial facilities) to its residents, thus requiring movements to and from nearby cities to access some services.
In general, villages are located in rural areas, however, modern urban neighborhoods are also termed as 'urban villages' in some countries. In this FAQ guidance is provided for villages located in rural areas.
Roads in towns and villages are primarily of two types: rural highways routed through towns and villages connecting these areas with urban areas, and local town and village roads which service the area and connect with the rural highways to access services and facilities within towns and villages. Roads within towns and villages need to ensure safe speeds for local traffic, including managing the greater risk that is typically posed by high speed traffic on major through roads, including rural highways.
Rural highways pose significant crash risks to road users on the highway and in towns and villages through which the highway is routing due to the high speed of motorized road users. When reaching a town / village along the highway, after a period of uninterrupted driving at high speed, drivers on rural highways generally underestimate their travelling speeds. This can result in severe crashes when these motorized vehicles encounter vulnerable road users, or local traffic.
These issues can be addressed through the following infrastructure engineering measures used to manage speed:
Rural highways through a town/village
→ Lower speed limits
→ Transverse rumble strips (especially as warnings for subsequent stronger speed managing infrastructure such as speed humps)
→ Textured surfaces
→ Repeater signs
→ Raised traffic signalized intersections
→ Transverse rumble strips
→ Raised pedestrian crossings
→ STOP or GIVE WAY control
→ Speed humps/cushions
Non-built-up areas outside of cities and towns include various road types and speed limits. The road types can vary from motorways, high-speed roads that connect major towns and cities, and lower volume rural roads. The speed limits can range between 90 and 120 kph on motorways and between 70 kph and 100 kph on other roads, and these higher speeds are considered safe where these roads are designed for motorized traffic, and fully segregated from vulnerable road users. Good quality infrastructure is required on higher speed roads to ensure safety. Examples of this infrastructure includes barrier systems, good alignment and cross-section, and well-designed intersections.
It is recommended that pedestrians and cyclists are fully separated from the high speed roads to eliminate interaction and risks e.g. non-motorized lanes or shared user paths. Where this is not possible, speeds can be reduced at key risk locations such as those approaching towns, villages or pedestrian crossings.
When it comes to speed limits, engineering measures should consider two things: the human body’s tolerance levels to the force of an impact and the various components of the highway. Listed below are a range of solutions to manage speed along highways:
o Vehicle activated signs
o Consistent treatment of curves along routes including chevron alignment markers, guideposts, warning signs etc. to provide road users with a self-explaining (see Question 3.8) level of curve severity
o Speed advisory signs
o Advance warning signs
o Rumble strips (away from residential areas to avoid noise pollution)
o Lane narrowing
o Wide medians
o Whether activated signs
o Rumble strips (away from residential areas to avoid noise pollution)
→ Gateway treatments when entering towns and villages (see Q3.4). Their purpose is to make it easier to identify entry within a town or village hence increasing compliance with the speed limit
A self-explaining road is one where the design of the road tells road users how to safely use it, including the required speed at which they should travel. Various road elements act as visual and physical cues for slower or faster travel. Narrower roadways, physical traffic calming measures, different road surface texture and other design elements give a clear message that slower speeds are required. Wider roadways (including where there are multiple lanes of traffic) give the impression that higher speeds are possible. Consistent application of such measures across different types of roads (especially roads with different road use function) creates clear guidance to road users on their expected behavior including the appropriate speed. It is therefore clear to motorists where low speeds are required, or where higher speeds might be safe.
For example, in urban areas with a high number of vulnerable road users (see Q3.2), a driver will adopt a low speed when effective traffic calming measures such as narrower roadways and raised pavement surfaces are implemented. When entering a town or village (Q3.4), a driver can be provided with a “gateway” type treatment, and supporting infrastructure throughout the town or village such as narrower roadways and raised pavement surfaces, especially where vulnerable road users are present. These designs encourage appropriate behaviors relating to safe speeds.
A 30 kph zone is a network of urban roads and streets where the speed limit is dropped from the default 50 or 60 kph to 30 kph. Sometimes, speeds of less than 30 kph are used at locations where there are high concentrations of vulnerable road users. Along with 30 kph zones, these are often referred to as ‘low-speed zones’ and areused to improve vulnerable road user safety. Such areas:
→ are mostly located in urban environments;
→ have significant residential, educational or commercial uses (or other land uses that create/attract walking and cycling);
→ have motorized traffic and non-motorized modes of transport mixed; and
→ have more of an access and active transport function than a traffic flow function.
A combination of speed limit setting, speed management tools, road infrastructure interventions and technology can be employed to ensure a maximum 30 kph zone functions safely and effectively. These zones are quite appropriate for residential areas, villages, markets, retirement villages, school zones, hospital precincts, around places of worship, dense urban areas with lots of walking and cycling activities, university hubs, public transport hubs and major train station zones, city centres and Central Business Districts (CBD) and wherever vulnerable road users, especially the elderly and children, are in presence.
That is mainly why the Third Global Ministerial Conference on Road Safety’s Resolution 11 recommends to:
“focus on speed management, including the strengthening of law enforcement to prevent speeding and mandate a maximum road travel speed limit of 30 kph in areas where vulnerable road users and vehicles mix in a frequent and planned manner, except where strong evidence exists that higher speeds are safe, noting that efforts to reduce speed will have a beneficial impact on air quality and climate change as well as being vital to reduce road traffic deaths and injuries.”
Widely implemented across the OECD countries, 30 kph zones are repeatedly shown to improve road safety outcomes for all road users, especially vulnerable road users. Follow these links to find more about the Australian, Swiss, Dutch, German, Norwegian, Finnish, Welsh and Scottish experiences.
Further information on ‘low-speed zones’ can be found here.
Road infrastructure, signage and road marking contribute to the decision-making of motorcyclists, their choice of speed, their risk of being involved in crashes, and in some cases, the severity of injury outcomes. There are some key road safety engineering solutions that are shown to reduce motorcycles’ speed and speeding incidents, and/or mitigating the severity of injury outcomes if a crash occurs:
Safe speed limits: The posted speed limits must be determined in alignment with survivable speeds for all road users. While, because of their extreme exposure to raw crash forces, motorcyclists are likely to suffer severe injury outcomes at almost any speed, adopting and enforcing Safe System speeds across the network will reduce the crash and injury risks.
Traffic calming for motorcyclists: Traffic calming devices including vertical and horizontal calming features can help reduce speeding incidents and road safety risk for motorcyclists. Special consideration is required for calming of motorcycle speeds, as riders may be able to traverse standard calming devices at higher speeds, or even ride around them. In addition, poorly designed traffic calming can be a source of danger to motorcyclists. It is safe practice to:
a. locate vertical traffic calming features such as speed cushions and raised platforms away from turning or braking areas for motorcyclists;
b. locate horizontal traffic calming features such as chicanes in a way that sudden and excessive deviations from a direct motorcycle travelling line are avoided;
c. ensure road marking traffic calming features such as rumble devices have adequate skid resistance and are away from the final braking area on the approach to a hazard; and
d. ensure road humps of all types are properly maintained because a damaged surface could cause motorcycle instability.
Read more about traffic calming measures for motorcyclists here.
High-risk locations treatment: Identifying and addressing locations and road lengths where motorcycle speeding or speeding-related crashes are an issue can prevent the recurrence of these crashes. Reviewing motorcyclist crash history, police reports, conducting site visits, measuring motorcycle speeds and the speeds of other vehicles (given these also impact motorcyclist safety as well), and assessing horizontal and vertical alignments are recommended.
Improved road alignment and delineation: Horizontal geometry, particularly in the case of successive curves, should be consistent with radius, compound curves should be avoided (or clearly signed), and adverse crossfall should not be used where a motorcycle’s operating speed is likely to be high. Better delineation helps drivers of motorcycles stay in their lanes, especially on bends, and avoid collisions. It should be noted that sometimes delineation devices themselves (such as paint and steel sign poles) become risk factors.
In addition to these solutions, there are several road safety infrastructure measures that could be used as complementary tools to motorcyclist speed management measures. Physical separation (dedicated motorcycle lanes), better surface friction and more effective roadside hazard management are just a few examples.
For more details on these main and complementary solutions see:
→ the Austroads’ guide ‘Infrastructure Improvements to Reduce Motorcycle Casualties’ (here);
→ a literature review by the Transportation Working Group of the Asia-Pacific Economic Cooperation (APEC) – ‘A review of potential countermeasures for motorcycle and scooter safety across APEC for project: compendium of best practices on motorcycle and scooter safety’ (here); and
→ a European study on powered two wheelers and safety measures, produced as part of the 2-wheeler behaviour and safety (2-be-safe) project (here).
Because speed limits and enforcement are intertwined, it is important for the road authority to liaise with enforcement personnel before setting a speed limit for a location. Enforcement personnel have experience and unique insights into the enforceability of speed limits that may be used to ensure that rational speed limits are applied. They also have local knowledge of the location of crashes and the locations where speeding is prevalent.
Enforcement is an important and necessary measure for speed management. In many countries speed enforcement has significantly evolved over the past 10 years with a general increase in the focus of enforcement efforts and the increasingly widespread introduction of automatic speed control, which does give a new dimension to the enforcement effort. If undertaken appropriately, speed enforcement can be a very powerful measure (deterrent) that contributes directly to reducing the incidence of speeding and consequently, the frequency and severity of crashes.
The objectives of the enforcement component are to:
→ Act as a deterrent to all road users which are more likely to disobey road rules and present a danger to others;
→ Maximize the effectiveness of enforcement activities by integrating them with engineering and promotional efforts;
→ Raise understanding of the importance of police enforcement;
→ Encourage the participation of the police in an integrated and comprehensive traffic safety strategy.
Enforcement can yield immediate and significant impacts. Not only is this important from a crash prevention perspective, but also essential to maintain the ongoing enthusiasm of the project participants. It can also complement and maximize the effectiveness of other measures e.g. infrastructure, education.
ETSC states “Since excessive or inappropriate speed is a primary factor in about one third of road deaths and an aggravating factor in many more, speed enforcement will remain essential as long as the speed problem is not solved in a structural way by road design, engineering measures and in-vehicle technology.” Link to the full report here.
Also, learn more about the effects of speed enforcement on road safety here.
In addition to detecting offenders, one of the major roles of enforcement in speed management is deterring unsafe behaviors. The level of deterrence is related not only to the actual level of enforcement, but also to the perceived level of enforcement and the perceived deterring value of the penalties. Publicity promoting enforcement can increase the perceived level of enforcement and thus further reduce unsafe behaviors.
General deterrence is the impact of the threat of legal punishment on the greater public at large, influencing a potential traffic law offender, through fear of detection without actual detection of that potential offender. Therefore, operations employing general deterrence mechanisms target all road users irrespective of whether they have previously offended. General deterrence programs have the potential to influence the behavior of all road users.
Specific deterrence is the impact of the punishment on those who are apprehended. Therefore, the potential impact of a specific deterrence program may be more limited than that of programs relying on the general deterrence mechanism. See here a study from Cameron & Sanderson (1982).
Thus, general deterrence results from the perception of the public that traffic laws are enforced and that there is a risk of detection and punishment when traffic laws are violated. Specific deterrence results from actual experiences with detection, prosecution, and punishment of offenders.
The general assumption underlying police enforcement is that it should primarily aim at general deterrence, which is first and foremost achieved by increasing the subjective risk of apprehension.
Covert, mobile speed camera enforcement programs may provide a more generalized deterrent effect and may have the added benefit that drivers are less likely to know precisely when and where cameras are operating. Speed enforcement activities are best repeated frequently, at irregular intervals and with different intensities. Higher intensities generally result in larger effects.
To maximize road safety effects, traffic law enforcement should, first and foremost, prevent violations that are proven to be linked to the number or severity of crashes (such as speeding). There is no single best method for enforcing speeds since different forms should be considered in different contexts. The following types of enforcement (manual or automated approaches), which should always accompany any change in speed limit, may be used:
→ Stationary patrols use marked or unmarked vehicles stopped at roadside to monitor traffic speeds.
→ Mobile patrols use marked or unmarked vehicles traveling with traffic to detect specific violators in the immediate vicinity of a moving patrol car.
→ Highly visible enforcement strategies use multiple stationary or mobile marked patrol cars to remind the public that enforcement is present and to increase the actual and perceived risk of detection among the driving public.
→ Stealth methods use unmarked, unconventional, or hidden vehicles to monitor speeds and apprehend speeders.
→ Automated speed enforcement (ASE) uses equipment that monitors speeds and photographs offenders to produce a citation that is later mailed to the registered owner of the offending vehicle.
→ Aerial speed enforcement from aircraft measures vehicle speeds based on the time it takes a vehicle to travel between two or more pavement markings spaced a known distance apart. Identifying information regarding a violator’s car type, location, and cited speed is transmitted to officers on the ground, who issue citations.
Evidence has shown that enforcement through the use of automated speed control is most-effective at reducing speeds. It is important to mention that where countries have changed their speed limits, but have taken little action to enforce them or the control speeds through engineering, there have been very limited benefits. You can read more about the effectiveness of speed cameras in preventing road traffic collisions and related casualties here.
Generally, the public perceives that there is a cushion or threshold above the speed limit in which officers will not cite offenders. In many countries enforcement practice usually allows for a threshold between 5-10 kph above the speed limit. While speed limits are legally binding, some tolerance is often applied in order to focus enforcement on the most dangerous vehicles. An officer is usually provided some discretion in whether or not to issue a ticket for a speed that is just a small amount over the speed limit. Because it is difficult to cite drivers who are operating a vehicle within a couple of kilometers per hour of the limit, most jurisdictions adopt an enforcement threshold either officially or unofficially. Law enforcement personnel, the courts, and the public should have a clear understanding of the enforcement threshold. Absolute “zero tolerance” enforcement is generally not feasible, but a very tight threshold is acceptable under limited circumstances.
Victoria, Australia has had success with a program that tightened enforcement tolerances as part of an overall speed management package that included automated and other enforcement, publicity, and penalty restructuring . You can read more about here.
Also, a recent experiment in Finland found that lowering the enforcement threshold of fixed speed camera enforcement on a rural two-lane road from 20 kph above the limit to 4 kph above the limit (advertised as zero tolerance) and publicity of the measure reduced mean speeds by 2.5 kph and speed variance by 1.1 kph in comparison with a similar, camera-enforced corridor where the threshold was not reduced (Luoma, Rajamäki, & Malvivuo, 2012). The percentage of vehicles exceeding the speed limit was reduced from 23% to 10%, so deterrence of speeding was increased without increasing the processed citations (police or administrative burden). The speed effect of the reduced threshold was within the range of effect of the initial implementation of the automated camera enforcement.
There are multiple reasons why speed enforcement works better in some countries than others, and some of them include:
Political will: A political environment prioritizing road safety, including speed enforcement, and providing adequate resourcing is an essential requirement. This prioritization varies immensely around the world. Even in many high-income countries, it is often challenging to convince the government of the importance of dedicating resources to speed management.
Crash and speed data: The lack of speed data and the under-reporting of crash data, particularly in low- and middle-income countries, is a significant issue and impedes the successful management of road safety overall, and speed management in particular. Without data, it is difficult or even impossible to select those stretches of road where speeding actually is a road safety issue and enforcement should take place.
Speed limits: Speed limits are the means by which legal sanctions can be brought to bear on those who drive faster than is appropriate and safe on the roads. Currently, speed limits vary across the world. Many road authorities in high-, middle- and low-income countries have no speed limits posted on their roads, consequently, the level of enforcement also varies.
Financial – The amount of funding dedicated to traffic enforcement varies greatly between countries. For many countries, leaders have not yet recognized or acknowledged the drain on health care and other costs and the positive impact that might be gained by enforcing speed limits, with the result of savings gained through fewer deaths and injuries resulting from speed-related crashes.
Human – Even in high-income countries, decision-makers often do not recognize the value of traffic speed enforcement, suggesting instead that there are other policing priorities.
Training of police – The importance of traffic speed enforcement for road safety and the collection and processing of crash data should be an integral part of police training.
Dedication of necessary financial and human resources to the traffic police is essential for ongoing speed enforcement.
Automated speed enforcement (ASE) systems are an important element in speed management and can be a highly effective countermeasure to prevent speeding-related crashes. However, ASE is a supplement to, not a replacement for, traditional enforcement operations. Advantages of ASE include: the ability to increase safety for law enforcement officers by implementing ASE in areas where traditional traffic stops are dangerous or infeasible due to roadway design, the ability to continuously enforce the speed limit (24 hours, 7 days a week), reduced opportunity for corrupt behaviors to avoid a legal penalty, and reductions in traffic congestion sometimes caused by driver distraction at traffic stops.
ASE is a tool that can enhance the capabilities of traffic law enforcement. ASE will supplement, rather than replace, traffic stops by law enforcement officers. The public should be made aware that ASE is used to improve safety, not to generate revenue or impose “big brother” surveillance. Saying this will not necessarily make it so in the eyes of the public, so it is important to explain how each element of the ASE program puts safety first and how controls are in place to prevent misuse of the system. ASE programs worldwide have demonstrated the ability to reduce speeding and crashes beyond the effects observed with traditional speed enforcement alone. Conducting evaluations to show that ASE has reduced deaths and injuries also helps sustain the position that ASE is for road safety, and helps sustain political will for ASE.
All ASE systems have three basic components: a speed measuring component, a data processing and storage component, and an image capture component.
Speed-Measuring - Speed-measuring requires the ability to detect and discriminate individual vehicles on a roadway and measure their speeds in real time. The accuracy of speed-measuring devices is crucial. Most speed-measuring devices are equally accurate measuring approaching or receding traffic speeds and are accurate to within 1 kph when used properly. Emerging technologies are expanding the versatility of speed-measuring devices and target vehicle discrimination. For instance, scanning lidar (a system that works in a similar way to radar, but by using the light from laser), allows lidar to be used on multiple lanes and two directions of travel simultaneously. Speed measurement devices must be calibrated and tested before their first use and then retested on a regular basis, preferably by an independent laboratory.
Data processing and storage - The data processing and storage component is a computer that receives data from the speed-measuring unit and compares the speed data against the threshold that was set to define violations in real time. If a vehicle’s speed exceeds the threshold, the unit identifies the vehicle as a violator and triggers the camera to photograph the vehicle. Additional information such as time, date, and operator-entered information is also recorded with the speed data.
Image capture - The image capture component includes one or more cameras that photograph the speed violation in progress when they are triggered by the computer. The photographs must include a legible image of the license plate and, if driver identification is required, a clear image of the driver’s face. A fast shutter speed and high image resolution are essential features. Digital photographs are easy to transfer and reproduce electronically, which can save time and effort during violation processing. However, extra care is necessary to ensure the integrity of photographic evidence.
ASE systems include:
→ fixed cameras, which continually monitor traffic speeds without an operator;
→ semi-fixed cameras, with cameras that are rotated between housings resulting in housings with active cameras and ‘dummy housings’ without cameras;
→ mobile camera operations, most often deployed in vehicles with or without enforcement agents present; and
→ average speed enforcement systems that measure average speed between two check points on a roadway, also known as speed and distance cameras or point to point cameras.
For additional information refer to NHTSA Speed Enforcement Camera Systems Operational Guidelines. For a guide to determine Automated Speed Enforcement readiness see here.
The following are some of the advantages and disadvantages of speed cameras.
For a guide to determine Automated Speed Enforcement readiness see here.
Speed cameras are an important part of overall speed management, leading to improvements in safety as well as other societal benefits. Speed cameras have additional benefits over traditional forms of enforcement due to the fact there will always be a shortage of police officers everywhere dedicated to traffic duties, especially dedicated to speed enforcement.
For a guide to determine Automated Speed Enforcement readiness see here.
Yes, the consistency of reported reductions in speed and crash outcomes across various studies show that speed cameras are a worthwhile intervention for reducing the number of road traffic injuries and deaths. Examples are presented below:
The Centre for Disease Control in the US identifies several evaluations showing the effectiveness.The best-controlled studies suggest injury crash reductions are likely to be in the range of 20 to 25 percent at conspicuous, fixed camera sites. Covert, mobile enforcement programs also result in significant crash reductions area-wide. See here.
In addition, the British Medical Journal reports the results of 17 observational studies on the topic. In these studies, reductions in outcomes ranged from 5% to 69% for collisions, 12% to 65% for injuries, and 17% to 71% for deaths in the immediate vicinity of camera sites. The reductions over wider geographical areas were of a similar order of magnitude as seen here.
The Cocrane Library also publishes a variety of research of the effectiveness of speed cameras in reducing speeds and reducing the frequency and severity of crashes. You can learn more here.
The simple answer is NO. Speed cameras are a supplement to, not a replacement for, traditional enforcement operations. In fact, there are some benefits to be gained from conducting manual enforcement. These include:
→ When a driver is stopped by a police officer, the driver receives immediate feedback on the infraction;
→ The Police can explain the risk of speeding to the driver and explain the importance of the speed limit and that compliance results in fewer deaths and injuries;
→ Clearly visible enforcement can increase others’ perceptions of being detected (increasing general deterrence);
→ The driver may be identified as a disqualified driver or a “wanted person”; (many career criminals have been apprehended through manual police checks); andIn addition, other offences may be detected -e.g. checks for breath test, driver license, vehicle safety, etc. in addition to other non-traffic crimes.
There are several steps that need to be considered when developing an Automated Speed Enforcement Program.
Legal authority is essential for ASE programs. While the benefits of these programs are widely recognized, there remain reasons why some jurisdictions are unable to proceed. These include:
→ Due process. Some critics have alleged that automated enforcement violates the right to due process.
→ Equal protection. Other critics argue that automated enforcement violates equal protection.
→ Privacy. Driver identification is also likely to raise concerns about individual privacy. Although some people believe that photographing the driver’s face is an invasion of privacy, the general opinion of the courts has been that driving is a regulated activity in a public space, and therefore photographing drivers is not an invasion of privacy.
b) Identify speeding-related safety problems
The first step in planning the operations of an ASE program is to identify the speeding-related safety problems and attitudes that the ASE program will be designed to address. Measures that reflect a speeding problem include speeding-related crashes, excessive speeds, speed variance, and citizen complaints. Speeding-related crashes are the most direct indicator of a safety problem at a particular location. With data on crash history and excessive speeds, it is possible to determine where the speeding-related safety problem is located.
c) Develop a strategic ASE plan
A strategic plan for ASE should provide the link between the ASE program’s overarching objectives (e.g., to reduce the occurrence of speeding and speeding-related crashes) and the short-term and long-term benchmarks that indicate the degree of success in achieving objectives (e.g., the amount of reduction in speeding and crashes at each deployment location). Although program objectives should be tailored to the specific speeding-related safety problem in the community, there are general objectives that all ASE programs should strive to achieve. These are identified in the NHTSA (National Highway Traffic Safety Administration) US – Speed Enforcement Camera Systems Operational Guidelines.
Additional objectives might be more specific to the needs or restrictions of the jurisdiction (e.g., “Reduce speeding in school zones”). Everyone involved in the ASE program must share these objectives and work to achieve them for the program to be fully successful. The strategic plan should emphasize that it is important to avoid rushing to begin enforcement and should consider the long-term direction of the program, including contingencies for future expansion and improvement. Most successful ASE programs started with a minimal ASE presence and expanded their programs as the public came to accept the technology and as program participants gained experience and improved operations.
d) Identify countermeasures
Enforcement is only one component of a comprehensive speed management strategy. It is essential that the strategic enforcement plan combines all the other components. Roles and responsibilities should be clearly delineated, and the purpose of each countermeasure should be explained to achieve buy-in from everyone who is involved in confronting the problems caused by speeding.
e) Obtain interagency and community support
ASE is an inherently cooperative venture. A committee or advisory panel of stakeholder representatives should be formed during the planning process to guide program development and ensure that stakeholders can provide input from their unique perspectives.
Depending upon the structure of the ASE program, there may be other people or organizations involved in its planning and operations, such as experts in technology, information systems, finance, and contracting. A vendor representative may also be involved after a vendor is selected.
It is also essential at the very outset to ensure the public understand this is a program focused in reducing speeding and relevant crashes and injuries, rather than a “revenue-generation” initiative.
f) Seek experience and lessons from managers of existing programs
No matter how well it is planned and managed, running an ASE program is a learning experience. All successful programs have adapted to changing situations and all successful managers have modified elements of their programs that needed improvement.
g) Determine nature of violation and penalty
Depending on existing laws, ASE violations can either be considered “point” offenses that are punishable by fines and license sanctions or non-point offenses that are only punishable by fines. If possible, policies should be consistent among neighboring jurisdictions that use ASE to avoid public confusion.
h) Identify enforcement equipment alternatives
As identified in question 5.1, ASE systems have three basic components: a speed measuring component, a data processing and storage component, and an image capture component. In recent years, some jurisdictions have begun to supplement photographic evidence with a video record of speeding violations. Video resolution and frame rate are not currently at a level where video could replace photographs for driver and vehicle identification.
i) Identify requirements and resources needed for ASE program
The final step in the ASE planning phase is to identify the functional requirements, equipment requirements, and personnel requirements for the ASE program, as well as additional resources that will be needed to support the enforcement effort. Requirements should be defined in as much detail as possible, with prioritization according to level of need. Although some requirements might remain unknown until the final arrangements are made with the vendor, it is important to begin to identify requirements early to be able to effectively communicate needs to potential system vendors.
Prior to implementing speed cameras (or other automated enforcement program) the GRSF Guide for Determining Readiness for Speed cameras and other Automated Enforcement should be reviewed.
Appropriate site selection is essential to achieve the highest level of safety benefits and to ensure the public that safety is the top priority of speed enforcement. The highest priority enforcement sites should be located where there is the greatest risk for speeding-related crashes, injuries, and fatalities.
Crash risk can be determined from reliable data on crash history, crash patterns (e.g., seasonal or time of day) and other factors such as the percentage of vehicles that are speeding or traffic volume. Risk can also be high where there is a lack of supporting infrastructure for the type of road use (e.g., the presence of pedestrians, but poor infrastructure provision) and high vehicle speeds. It is generally unwise to select sites where speeding is common and risk is low because the public is likely to perceive these locations as “speed traps.” However, exceptions may be made in locations with many pedestrians and in neighborhoods where speeding adversely affects quality of life.
Citizen complaints can also help to identify locations with speeding-related safety problems. Responsiveness to citizen complaints is important because citizens may be the first to notice a developing safety problem and because speed enforcement is ultimately for the benefit of the (local) public.
A site should be defined either as one specific location or as a corridor with multiple enforceable locations. In general, defining a site as a corridor can be expected to result in a more widespread deterrent effect because enforcement locations are less predictable. Sites clustered in particular neighborhoods can provoke charges of biased operations or targeting of particular groups.
Other considerations might include:
School zones are frequently selected as locations for speed cameras and where this has occurred the public response has been positive. High-level support might make school zone enforcement a good way to introduce speed cameras in a jurisdiction.
Residential neighborhoods typically have low traffic volumes and low speed limits. Speed cameras should only be introduced at locations where speeding creates a safety problem or has a negative impact on quality of life, but within this constraint, public demand for speed management can influence site selection. It is important to have support from the residents of neighborhoods where speed cameras are used. School zones are one such example.
Major roads or arterials are often among the most dangerous roads in a jurisdiction, with high traffic volumes, high traffic speeds, and complex roadway geometries and traffic patterns. Speed cameras can have a significant impact on major roads, but factors such as multiple lanes of traffic and close proximity of vehicles can make it more difficult for speed cameras to single out speeding vehicles.
Roadwork zones often feature complex and transitory traffic patterns that increase the level of risk for road users and road workers. Voluntary compliance with reduced work zone speed limits is often low. Speed cameras may be especially helpful in work zones because they can be used in places where traditional enforcement methods are infeasible or hazardous.
Vehicle technology plays a significant role in speed control. Major advancements have been made in automotive technology that have greatly enhanced vehicle safety through speed management. Speedometers were the first devices installed in this regard, whereas modern vehicles are equipped with more advanced technology, such as Adaptive Cruise Control, Electronic Stability Control, and Intelligent Speed Adaptation.
Some of the primary devices, often tailored to vehicles to boost speed enforcement, are briefly presented below:
→ Speedometer: The speedometer, one of the first in-vehicle devices to track speed, is important for the driver to maintain the desired speed, particularly for speed limits.
→ Speed limiters (SL): Speed limiters, commonly known as Governors, are used for the setting of road speed in commercial vehicles. SL are pre-programmed to prevent a vehicle engine from exceeding a maximum speed. SL could be helpful in limiting bus and truck speeds, especially in rural areas where over-speed is most frequent due to lack of enforcement. Further information is provided in Q6.3.
→ Conventional Cruise Control (CCC): CCC is a technology that can help automatically maintain and regulate a vehicle’s speed as set by the driver. It responds by continually changing the fuel supply to sustain the speed generated by wind, rolling resistance or the gradient. It reduces driver workload as less concentration is required for speed control and maintaining the speed within the expected range.
→ Adaptive Cruise Control (ACC): ACC is a modern CCC version that utilizes radar or laser sensors for detecting and tracking vehicles in front and adjusting to their speed. In addition to choosing cruise speed, it allows drivers to change the time gap and headway in the travel lane with the front vehicle. Further information is provided in Q6.4.
→ Intelligent Speed Adaptation (ISA): ISA is a speed management device that utilizes cameras and/or an in built GPS map to determine the speed limit of the road to provide warnings and/or limit the speed of the vehicle if the speed limit has been exceeded. ISA is increasingly used as standard in new vehicles and will be mandatory in Europe from 2022. Further information is provided in Q6.2.
Click here to explore these technologies further.
Intelligent Speed Adaptation (sometimes Intelligent Speed Assistance, or ISA) is one of the most promising IT systems for its potential effect on safety. ISA is an intelligent speed control system utilizing data from the road environment and vehicle. The vehicle receives and responds to the desired or legal speed limit from the area. The system uses a digital in-vehicle road map to encode speed limits, together with a navigation system such as the Global Positioning System (GPS) satellite and/or traffic sign recognition. ISA could be three types in total: informative, voluntary supportive, and mandatory supportive.
Field and driving simulator experiments of ISA show positive effects on speed management and predict significant safety benefits. According to Várhelyi and Mäkinen (2001), ISA was found to be effective in reducing the speed in roads with 30-70kph speed limit. Carsten and Tate (2005) showed that mandatory use of supportive ISA could reduce the serious crashes up to 50%. The safety benefits of voluntary ISA are much smaller. It was demonstrated by Swedish and Dutch research that speeds were slower and more uniform when using ISA. In Britain, assessment of ISA system for trucks also provided positive evidence of safety benefits with respect to greater speed compliance.
Recently, ISA effectiveness was also assessed by The University of Adelaide Centre for Automotive Research based on real word crashes. It was found that ISA can result in substantial reductions in impact speed in a crash, and if all vehicles were fitted with ISA fatal and serious injuries would be reduced by 17.6% with limiting ISA, 8.1 to 12.3% with supportive ISA, and 5.1 to 9% with advisory ISA. The benefits and also the limitations of ISA are shown in the study “Intelligent Speed Adaptation (ISA): benefit analysis using EDR data from real world crashes”.
Some studies mention the negative side effects of ISA, but the scale and implications of these potential negative side effects are still limited. However, research has identified that the driver may become less vigilant, more confident/ frustrated or show compensation behavior in a few instances.
ISA is one of the vehicle safety technologies included in the EU’s new General Safety Regulation for motor vehicles (GSR) and will become mandatory for all new vehicles types as of 2022 and all new vehicles as of 2024.
Speed limiters (SL), commonly known as speed governors, are pre-programmed devices that interfere with a vehicle engine to prevent it from exceeding a maximum speed. It has been found to be beneficial on trucks and buses for the setting of road speed. Since SL capability is standard, the cost of introducing SLs is negligible.
The effectiveness was broadly assessed by Hanowski, R. J. et al. (2012), who showed that SLs are effective in reducing speed-related crashes. UK Analysis found that the rate of crash involvement for SL trucks dropped by 26%. Australia estimated a crash reduction of 29% involving trucks in this case if SL regulations are in force.
SLs cannot fix speeding on roads with speed limits lower than the top speed the vehicle is set at, and the literature shows that travelling too fast for the conditions tends to be an issue in these circumstances. Traffic consequences have also been reported as a problem in some places, such as the United Kingdom, owing to the long-distance needed for one SL truck to pass another. However, the negative effects of the SLs tend to be greatly outweighed by the safety gains associated with the decrease in total speed of the SLs.
To know more about this click here.
Adaptive Cruise Control (ACC), a modern edition of Conventional Cruise Control, utilizes radar or laser sensors for detecting and tracking the speed of vehicles in front and adjusting speeds based on this. In addition to choosing cruise speed, it allows drivers to change the time gap and headway in the travel lane with the front vehicle.
ACC utilizes forward collision warning (FCW) system technology. This is an advanced safety technology that monitors the speed of a vehicle, the speed of the vehicle in front of it, and the distance between the vehicles. The FCW system will warn the driver of an impending crash if vehicles get too close because of the rear vehicle's speed. More than just warning, when available, the Autonomous emergency braking, known as AEB, engages the main braking system when it detects an imminent crash. The findings showed a 38 percent overall reduction in rear-end crashes for vehicles fitted with AEB compared to a comparison sample of similar vehicles. There was no statistical evidence of any difference in effect between urban (<= 60 km/h) and rural (>60 km/h) speed zones. More information about the AEB efficiency is available here.
Research has identified that, when applied , ACC will limit traffic speed variations. More uniform speeds have been found to reduce the likelihood of the crash.
Chira-Chavala and Yoo (1994) analyzed crash data and identified that ACC may be a potential countermeasure for 7.5 % of crashes. Research by Rudin-Brown and Parker (2004) also indicates, however, that drivers may become excessively dependent on ACC as they become used to its service, raising the risk of a crash.
Click here for further information.
There are various in-vehicle speed monitoring devices which are currently deployed in modern vehicles. Those devices record several parameters to improve safety. The available in-vehicle Speed Monitoring Systems are provided below.
→ Event data recorders (EDR): EDR, widely known as "black boxes" that record many parameters before, during and after a crash, including vehicle speed. According to the research of Lehmann et al 1998, and Toledo et al 2008 the adoption of EDR can trigger substantial changes in driver behavior, including reduced speed and lower crashes if the driver and employees are aware about the device installation.
→ Tachographs: This device tracks the speed, the overall distance travelled between the stops and the resting periods of a vehicle for the entire trip. Mechanical tachographs are commonly used in professional driving, particularly in heavy goods vehicles. They are used by the police and transport operators to monitor the amount of continuous driving and resting hours, as well as the maximum and average speed during a trip. Electronic tachographs are increasingly fitted on commercial vehicles voluntarily, which allow real-time speed monitoring, report service hours of drivers and other parameters, and track freight.
→ Speed monitoring devices: This system gathers information related to an insured risk, including distance driven, speed, and travel distribution by day and day of the week. Advanced speed monitoring system consist of GPS technology which assists to monitor vehicle speed by dynamic tracking. Advanced data recorders can continuously record speeds and link them to speed-limit databases, tracking speed in real time.
Please click here to explore these technologies further.
Education, training, communication and promotion campaigns are essential elements of a comprehensive speed management policy. They are clearly focused on achieving safe driver behavior and improved road safety outcomes. They make a contribution to the improvements that a comprehensive speed management approach can deliver and complement the specific measures taken including those related to safer infrastructure, clearer and more consistent signing, vehicle safety and enforcement.
Mass media campaigns, coupled with enforcement and educational activities can lead to greater overall effectiveness in reducing speeding. The content of the messages should be based on risk and consequences, as well as aligning with improved or expanded enforcement processes. If campaigns are used to complement the enforcement activities, this should also be evaluated, outlining how the campaign contributed to the overall reduction in speeding.
Commercial advertising can also be in conflict with road safety goals. Advertisement campaigns produced for car manufacturers often promote high performance and high speed as a positive value; a way to enjoy driving more.
The pros and cons of public awareness campaigns have been frequently studied. This report (see link here) provides new insights on how to maximize road safety campaigns’ effectiveness.
Education delivers knowledge and training delivers skill, however the evidence so far does not indicate how these influence drivers’ perceptions of risks and consequences. Studies of most post-license driver training programs have shown to be ineffective and sometimes harmful to road safety. One of the main reasons for this is that any benefits gained through this knowledge and skill are outweighed by a greater risk from overconfidence following the training.
The goal of community engagement is to develop and enhance their participation in road safety and decision-making and raise awareness within them of their own personal behavior in contributing towards improved road safety. The City of Surrey, Canada engaged the public in dialogue with respect to lowering speed limits through their website found here.
Community engagement is also important in that the local community is more likely to accept the change in speed limit and subsequent enforcement of this if they are made aware of the risks and benefits of speed effective speed management. There are also examples where decision makers have supported speed limit changes due to community pressure, and this comes from increased community engagement, including through the efforts of NGOs.
The role of the community in supporting speed enforcement can be described under three basic approaches, which range in terms of the extent to which they are able to support the traffic police, the level of commitment involved, and their independence.
a) CONSULTATION - is the logical starting point for improving collaboration between local residents and the police. Local residents can assist the traffic police by providing additional information on the location and circumstances of unreported crashes, as well as on locations where crashes are ‘waiting to happen’, and where offences such as illegal turns or speeding, are a problem.
b) VOLUNTEERS - Local residents interested in assisting the traffic police on a more regular basis can volunteer on such programs as traffic wardens and school patrol programs.
c) PARTNERSHIP INITIATIVES - Potential partners include:
→ Community members
→ Neighborhood or community association members
→ Local businesses, including the Chamber of Commerce
→ Local pedestrian, bicycle and safety advocates
→ Groups representing victims, including families of loved ones lost/injured
→ Groups representing people with disabilities.
VicRoads has prepared a general guide for engaging the community and stakeholders in local road safety plans. It can be found here.
It is important to use a strong communications campaign including marketing and media to explain the philosophy and strategy behind a Speed Camera program. A speed camera program should be described as a tool that can enhance the capabilities of traffic law enforcement and that speed cameras will supplement rather than replace traffic stops by officers.
The public should also be made aware that speed cameras are used to improve safety, not to generate revenue or impose “big brother” surveillance. Saying this will not necessarily make it so in the eyes of the public, so it is important to explain how each element of the speed camera program puts safety first and how controls are in place to prevent misuse of the system. Engaging the media early in the process can help gain public support for the speed cameras, as the program develops. A comprehensive communications campaign is essential to maintain positive public relations and to ensure that the public understands how speed cameras work and why it will improve safety as a supplement to traditional enforcement. The campaign should begin in advance of the introduction of speed cameras, providing frequent updates throughout the planning and implementation stages. The two most important goals of the communications plan are to maximize public awareness and acceptance of the speed camera program. Data should be evaluated to identify at-risk drivers in the community. Special attention should focus on males and young drivers.
To achieve speeding deterrence, the public must be aware of the speed camera program and how it works. The public should be educated about the speeding problem and how it affects their community. Current efforts in traditional enforcement should be highlighted, including an explanation of how speed cameras will supplement the effort to make the community safer, decrease traffic congestion, and improve quality of life. An explanation of how the technology functions, successes in other communities, and how it is implemented should be included. The number of enforcement units in use, whether they are mobile or fixed, the types of sites that are enforceable, and the total number of enforceable sites should be explained. It is also possible to make public the specific locations of sites, though it would be unwise to reveal the schedule in advance of their deployment. Identifying all potential locations may have a positive effect on deterrence at problem locations if drivers know where enforcement is frequently located.
Revealing enforcement locations also contributes to the goal of program transparency and might appease some critics of the program, though public awareness of enforceable sites may reduce the general deterrent effect of speed cameras. It is also important to inform the public about the procedures for violation processing, payment, and adjudication. The public should be made aware of the penalties for speed camera violations and their rights and options if they receive a violation notice.
The State of Victoria promoted the use of camera technology through a comprehensive website located here.
The simple answer is no. Mass media advertising is often the most visible component of a campaign, however, to be effective, this must be combined with visible government and/or community support, particularly law enforcement. The effectiveness of publicity campaigns when they are combined with highly visible enforcement has led to substantial reductions in drunk driving in Australia and Europe.
For example, publicity about the number of deaths and injuries caused by speeding, combined with information about how lower speeds reduce the number of deaths and injuries, may change attitudes to speeding, or make lower speed limits and higher penalties for infringements more acceptable. While the presence of traffic law enforcement is essential, supporting campaigns are vital in elevating the profile of speeding as an issue which is legitimate for the police to pursue and to make drivers aware of the consequences of this activity.
Research in many countries has shown that a publicity campaign by itself has only a modest impact on attitudes and behavior. Campaigns work best when combined with other interventions, such as enforcement of traffic laws and regulations, or provision of other safety services and products. A “behavior change” campaign must include enforcement. Social media is most important in reaching younger people. It is important (and valuable) to use social media as a way to engage people in the campaign, rather than as a one-way communications channel. For example, you can encourage followers and partners to share, re-tweet and like your campaign messages and visual content like photos, infographics and film clips, to promote the campaign to a wider audience. You can also invite people to give their views on the campaign topic and feedback on how the event went, and post their own pictures and film clips.
For more information, you can consult this resource in addition to the the recently published GRSF guide for Road Safety Interventions: “Evidence of what works and what does not work”.
In the late 1960s & '70s, the Netherlands was far from being an acknowledged leader in pedestrian and cyclist safety as it is today. Road deaths numbered in the thousands, and as documented in Road deaths in the Netherlands, hit a ceiling well above 3,200 per year. Cyclists, pedestrians, and children paid most of the price.
This triggered the historic ‘Stop de Kindermoord’ (literally "Stop the Child Murder" in Dutch) grassroots movement in the Netherlands. The success of this movement turned Dutch government policy around and the country began to restrict motor vehicles in its towns and cities and direct its focus on growth towards walking and cycling.
Since then, a large number of grassroots advocacy groups, established on similar lifesaving agendas, have emerged around the world, some of which are focused on speed management.
20's Plenty for Us is a 'not for profit' initiative with 500 local groups campaigning to make cities, towns, and villages around the world better places to be. They campaign for a default speed of 20 mph (30 kph) on residential streets and in town and village centers, without the need for physical calming. Local circumstances may make a higher limit appropriate on some streets, providing that the needs of vulnerable road users have been fully considered.
Love 30 Canada is campaigning to make 30 kph the default speed limit for urban and residential streets. They state that no matter how safe vehicles, roads, and drivers are, all of these things will fail beyond certain speeds. Each road must be designed to have speeds that are in line with the injury potentials on each type of road in the event of a crash. The level of harm to vulnerable road users rises dramatically at speeds of higher than 30 kph, making this the sensible default limit for places where vehicles and people mix.
30please are campaigning for 30 kph speed limits to be the norm for neighborhood streets. They demand a strategy to create safe and connected walking and cycling network. They believe sharing existing streets by driving slowly on those that are not very important for cars is a sensible solution, not only from a cost perspective.
Speeding and travelling too fast for the conditions are the biggest cause of death and serious injury on our roads. This is perhaps also the area where we have the clearest evidence base regarding this risk relationship. Much of the published research indicates that speed contributes to around 30% of deaths, but it is also frequently recognized that this is likely to be an under-estimate. We know this because when appropriate speed management is put in place, we see reductions of 60% or even greater in deaths and serious injuries.
The good news is that even small reductions in speed can have a substantial reduction in fatal and serious crash outcomes. As outlined in Q1.5, just a 1% reduction in speed can produce a 4% reduction in deaths on the road.
There is good news: Generally speaking, lower speeds have actually positive effects on congestion. Still, fighting congestion effectively and sustainably is a very difficult task as drivers’ travel patterns are often repetitive and added capacities are normally rapidly consumed by induced demand and population growth.
There are two types of traffic congestion: recurring and non-recurring. About half of traffic congestion is non-recurring and caused by ‘temporary disruptions’ in travel, e.g. due to bad weather, road closures, vehicle crashes or break-downs. Higher speeds will lead to more crashes and thus increase non-recurring congestion.
Recurring congestion happens in regular intervals (rush hours) and is due to a lack of capacity on the road — or in other words, there are more vehicles travelling at a given time than can physically fit. When this happens, vehicles are likely to already be travelling well below the speed limit, so a reduction in speed limit is not likely to affect speed during congested hours.
In busy urban environments the average journey speeds are often already considerably lower than the set speed limits. Travel time is mostly influenced by frequent stopping or slowing down, e.g. at intersections or at railway crossings. Drivers assume that driving faster will reduce overall travel time, which is not true in urban environments. Traffic moves most smoothly at a speed of 20-30 kph. The following-distance between cars may be shorter at lower speeds, but it still allows traffic from side streets to filter in and encourages the continuous movement of traffic. A speed of 30 kph allows the road system to smoothly accommodate the maximum number of cars (more cars than at higher speeds). Thus, lower speed limits generally mean less recurring congestion and faster overall travelling time for all. In a world where time is money, this is a significant advantage.
Furthermore, traffic congestion in urban areas is a major consideration for assessing various modes of transport. Lowering speed limits will encourage more walking and cycling, and – given that an adequate walking and cycling infrastructure is provided – this shift will free up capacity to your roads, reduce the strain on public transport and has positive effects for the environment.
From a road safety perspective increasing traffic speeds is generally is a very dangerous idea (unless the infrastructure fully supports the change). Even rather small increases in speed dramatically raise the number of people killed or seriously injured in road crashes.
High speeds reduce the possibility for the drivers to respond in time when necessary. People need time to process information, to decide whether to react, and finally, to execute a reaction. At higher speeds the distance covered in this period as well as the distance between starting to brake and a complete stand still are longer. Therefore, the possibility to avoid a crash becomes smaller as speed increases.
Another very important aspect is that more kinetic energy must be absorbed during a high-speed impact. The kinetic energy during a crash greatly increases due to velocity rather than mass and consequently, small increases in vehicle speed will result in major increases in the risk of injury.
Thus, higher speeds not only increase the likelihood of crashes (see Question 1.6) but also their severity. Sound scientific relationships have been established between speed and crash risk: The general relationship is valid for all speeds and all roads, but the rate of increase in crash risk varies with initial speed level and road type.
Furthermore, large speed differences between different types of vehicles – for example between faster cars and slower lorries on an expressway – also increase the likelihood of a crash. Higher speed variance results in less predictability, more encounters and more overtaking maneuvers. The probability of a rear-end crash with a slower car in front, or a head-on crash when overtaking a slower car increase. Therefore, when speed differences increase, the crash risk increases as well.
The good news is that even a small reduction in the mean speed reduces the number of crashes and the severity of injuries. In this context the more severe crashes get influenced the most.
The following tables show the impact of a 1 kph and 2 kph average speed reduction, respectively, on the severity of crashes for roads with different reference speeds. The reference speed is the ‘original speed’ driven on a road before a change in speed.
The tables clearly show the importance of even small reductions in average speed on the severity of crashes. On slower roads, typically in urban areas, the impact of a small speed reduction is generally bigger. However, the relationship between speed and crashes on a particular road will also depend on other factors such as traffic characteristics and road user behavior (drink-driving, seat belt wearing etc.).
You want to know more? Click here.
Often a traffic sign might not be enough to convince the road users to actually drive at or below the posted limit. It is often the case that drivers do not respect these limits – despite being aware of them – mainly because for the drivers seemingly identical roads have different limits.
There are many different ways to encourage people to drive at lower speeds, but evidence shows that self-enforcing speed limits are the most successful way to reduce speeds. A self-enforcing speed limit means that people are more likely to drive within the signed speed limit because they feel it's the easiest and safest speed to drive along that road. This is generally because of the way the road looks and has been designed. Engineering treatments have to be applied in addition to the speed signs to encourage – or force – the drivers to drive more slowly. A wide range of engineering solutions (see question 3.1) are available that have the effect of making it impossible or uncomfortable to drive in excess of the legal or recommended speed. But even in those cases where the speed sign is the only measure there is at least some good news: A new (lower) posted speed limit usually leads to at least some reduction in speed (typically around 3 kph for every 10 kph reduction in speed limit) – and even these small reductions in speed equate to substantive safety benefits (learn more in question 1.9).
A lower speed limit may indeed impact the economy, but in a positive way. Drivers often assume that the faster they drive, the quicker they reach their destination. However, the cost of this assumption is high to the driver, to the driver’s family, to the insurance companies, government agencies and hospitals involved in caring for the trauma victims. The WHO Global Status Report on road safety (2018) confirms that the most impacted age category from road trauma is between 5 to 29 years old. Losing young people of working age impacts the economy. Costs related to injury and loss of life from traffic crashes as a result of excessive speed include the following:
→ Medical costs: money hospitals need to pay to treat injuries
→ Productivity loss: production loss can be calculated as loss of hours worked
→ Property damage: vehicle repair costs
→ Settlement costs: insurance or third-party costs
→ Congestion costs when a crash occur.
The opposite is also true. High speeds may have a positive impact on economy. High function roads, such as motorways and freeways, with few access points, moving a high number of people and goods, connecting across multiple cities, can have a higher posted speed limit. In such circumstances, the infrastructure measures will need to be supportive of high speeds so that where a crash occurs it shall not result in a fatality or serious injury.
Individual and collective risk at high speeds are different. At an individual level, the risk of being involved in a crash resulting in a fatality or serious injury is relatively small. Collectively, at a community level, the risk of excessive speed is well documented as being a major contributor factor to road trauma. Therefore, balancing the individual and the needs of a community as a whole is a challenging task and a difficult argument from an economic perspective.
Many evaluation studies clearly show that speed humps and rumble strips produce positive road safety benefits. Both elements are often used as part of a broader area-wide speed management approach.
Transverse rumble strips, which are laid across the road, can alert drivers to hazards ahead (e.g., intersections, bends, or areas with pedestrian activity), thus slowing them down. They may also be used as part of a gateway treatment at the entrance into a town or village to make drivers aware of the fact that they are about to enter a built-up area and decrease their speed accordingly.
Longitudinal rumble strips, which are laid in the direction of travel either on the centerline or the edge line, can assist vehicles in keeping within their lane and may also be used to optically narrow the road and thus encourage drivers to slow down. Rumble strips do indeed induce higher levels of noise as vehicles pass over the strips. Thus, rumble strips are normally not used in residential areas.
Speed humps are very effective in slowing drivers down, especially in urban areas and locations with pedestrian traffic. If carefully designed and placed with the correct height, ramp profile, and width they result in minimal disruption for residents in terms of noise. It is essential that speed humps be well marked and signed in advance so road users are aware of their presence and prepared to slow to an appropriate speed. Lack of appropriate warning, especially in higher-speed environments, can create a road hazard, leading to issues such as instability of vehicles (especially motorcycles).