- Integrating Safety into Road Design
- Safe System Guiding Principles to Safer Design
- The Role of Road Design Guides
- About This Guide
Integrating Safety into Road Design
This guide focuses on elements of safe road and roadside designs for road networks that can provide safe mobility to all road users
A substantial reduction in road deaths will only be feasible if concerted efforts are made, following the “Safe System” approach involving all elements of road safety, management, and delivery. This includes all pillars of the Safe System—starting from road safety management, safe roads and roadsides, safe speed, safe vehicles, safe road users, and post-crash care. This guide focuses on elements of safe road and roadside designs for road networks that can provide safe mobility to all road users, as well as complementary changes to improve speeds, vehicle safety, road user behaviors, and post-crash care. A balanced road design must take into account these complementary system elements to maximize safety benefits. The energy carried by a moving object is proportional to the square of its speed. A well-designed “forgiving roadside” ensures that this energy is dispersed in a crash, and as a result, less energy is transferred to the occupants.
Road infrastructure design plays a vital role in road safety outcomes. Safe infrastructure supports other road safety pillars by encouraging appropriate road user behavior (such as appropriate speed and correct lane position) and by providing a forgiving road environment if things go wrong. Poorly designed road infrastructure can give rise to dangerous road user behavior. One of the key realizations of the Safe System approach is that drivers make mistakes and will continue to do so, even if we can reduce how often these occur. This road user error has long been recognized as a significant contributor to poor road safety outcomes. However, roads of any given speed can be designed to reduce the likelihood of crashes occurring, and there is very clear evidence that the severity of outcomes when crashes do occur is significantly influenced by the road design. Even if a crash still occurs, improved road infrastructure can save many lives and prevent debilitating injuries.
The Safe System approach highlights that a shared response is required to address road safety. This means that road users will continue to take responsibility for their actions, for instance by being alert and compliant with road rules. However, it is also recognized that road managers and designers have a significant responsibility to provide a road system that protects all road users. This can be achieved through appropriate designs of roads.
Did You Know?
Safe road infrastructure can reduce deaths and serious injury of up to 80 percent, and are possible by installing appropriate barrier systems and ensuring that these are adequately maintained.
Safe System Guiding Principles for Safer Designs
The following Safe System principles are recommended to ensure safety in sustainable road transport system design:
Road design needs to be for all road users—not only for motorized vehicles. The implication of this is that designers need to cater for the most vulnerable road users present. In doing so, safety will typically be improved for all road users.
Roads serve two primary functions or “roles”: to facilitate the movement (mobility) of people and goods and to act as places (access) for people. For safe design the “actual function,” not the “intended function” should be identified. In cases where mono-functionality cannot be realized in the short term, efforts should be made to provide adequate safety through safe speeds, starting with provision for the most vulnerable road users.
Design should meet road users’ expectations and be free from any surprise to road users. In case of practical limitations, clear delineation (e.g., markings and signs), adequate sight distance (e.g., decision sight distance), and/or speed management should be used to provide safety for all road users. In addition, variations in key design parameters along the road have an impact on traffic flow and safety. Such transitions should be supported by safe speed reductions, for example, traffic calming. This is applicable in case of variation in cross-section design near bridges/culverts, for roads passing through villages and towns, at-grade crossing facilities for vulnerable road users, and so forth.
Design should limit differences in vehicle speed, direction of travel, mass, and size. The design should ensure that vehicles (road users) travelling at different speeds are not able to interact (e.g., fast moving cars and vulnerable road users); that those travelling in different directions are not able to collide, especially at higher speeds, (for example in head-on conflicts), and that road users of different mass or size do not mix (for instance, trucks and vulnerable road users). Where it is not possible to provide designs that ensure separation, speeds need to be low.
Design should support Safe System speeds. The determinant of “safe design” is the safety of the most vulnerable or least protected road user and their tolerance to impact forces during a collision. This survivability is largely dictated by the impact speed for different road users. Hence, similar to “design vehicle,” the concept of “design road user” should be adopted to ensure safety, especially when considering the speed environment.
Roads and roadsides should be forgiving, i.e., free from hazards. In higher speed environments roads and roadsides should be free from permanent as well as temporarily fixed objects, such as rigid structures, trees, stopped/parked vehicles, etc., and should be protected if vehicle departure is non-recoverable.
Design needs to minimize exposure to risk for all users. This can be achieved at the planning stage by providing good quality, safe infrastructure that encourages modal shifts (e.g., from motorcycles to mass transit systems in cities). Exposure to risk can also be managed through the provision of safe infrastructure elements. As an example, intersections can be designed to remove or eliminate exposure by banning turning movements across multiple lanes of traffic.
Road design should be done in a way to support other elements of the Safe System. For example, it may be possible to build post-crash response into the design (e.g., providing shoulders to park disabled vehicles or access of emergency vehicles, providing for safe enforcement activity).
The provision of safe road infrastructure relies on good decision-making by recognizing key risk factors while planning road infrastructure and incorporating appropriate design elements to address these risks by understanding the key crash types that result in deaths and serious injuries.
Typical Road Design Risk Factors
The GRSF report contains a number of typical road design risk factors and recommendations.
|Risk factor||Motorways||High-speed inter-urban roads||Urban, residential, and village roads||Go to section:|
|Inadequate sight distance or line of sight is obstructed with unplanned roadside construction|
|Missing, insufficient, or incorrect safety barrier installations (both roadside and centerline)|
|Poor combinations of horizontal and vertical alignment, in particular “hidden dips”|
|Presence of rigid objects by the roadside posing hazards|
|Insufficient drainage leading to water logging or deep open drainage ditches posing risk|
|Cross-section with wide, hard shoulders which are (wrongly) regularly used for overtaking|
|Inconsistent radius sequence of consecutive curves, e.g., sharp curve after a sequence of significantly more gentle curves, erroneous compound curves with high variability of ratio of the radius, broken back curves, etc.|
|Unsafe routing and insufficient protection of pedestrians, cyclists, and motorcyclists along the road and intersections, including missing/insufficiently separated pedestrian and cyclist facilities from high-speed traffic and missing/insufficient crossing facilities|
|Inadequate skid resistance|
|Lack of climbing lanes in steep upward grades on two-lane roads|
|Insufficient superelevation on bends leading to high risk of lateral shift or overturning|
|Lack of strong and stable verges|
|Signal controls that do not consider the needs of all road users, including excessive delays for pedestrians and cyclists|
|Lack of protection for left-turning movements in right-driving traffic, and right-turning movements in left-driving traffic|
|Inappropriate road widths and cross-sections in built-up areas, e.g., wide road/lane widths at the expense of facilities for vulnerable road users|
|Narrow lanes on high-speed roads, curves, and turning lanes|
|Inappropriate parking and loading facilities|
|Missing/ineffective traffic calming measures|
|Lack of visual contact between motorists and pedestrians/cyclists|
|Poor recognition of intersections and rights of way due to a lack of guiding features, e.g., channelization, markings, and signs|
|Inadequate signage and pavement markings|
Download Report Chapters
It is not the intention that readers will read this guide from cover to cover. For your easy reference, please refer to the relevant chapters below:
- General Road Design Principles
- Road Function and Land Use
- Vehicle and Road User Type in LMIC Context
- Context Sensitive Design
- Community Engagement
- Design speed and operating speed
- Speed Management and Traffic Calming
- Sight distance
- Linear Settlements
- Access Control
- Construction, Operation, and Maintenance
- Pedestrian Facilities Design—Footpaths
- Pedestrian Facilities Design—Crossings
- Cyclist Facilities Design
- Motorcyclist Facilities Design
- Public Transport—Bus Stops; Bus Rapid Transport and Other Modes
- Road Width
- Shoulder Width and Type
- Horizontal Curvature
- Superelevation and Cross Slope (also referred to as “camber” or “crossfall”)
- Vertical Curvature and Gradient
- Passing Lanes
- Roadsides—Forgiving Roadsides and Clear Zones
- Road Surfacing
- Road Signs
- Line Marking
- Street Lighting
Good design practice/treatments/solutions
- Uncontrolled and Unsignalized (yield) Intersections
- Signalized Intersections
- Raised Intersections
- Channelization (including turn/slip lanes)
- Left-in Left-out/Right-in Right-out
- Acceleration and Deceleration Lanes
- Grade Separation and Ramps
- Rail Crossings
- Road Infrastructure Safety Performance Indicators
- Infrastructure Tools and Techniques
- Key reference documents
Frequently Asked Questions
This document is intended to provide easy access to information on road safety as part of the road design process. It is especially relevant for those working in low- and middle-income countries (LMICs), although the information will benefit all countries. The guide should be used to inform LMIC clients, road designers and practitioners involved in road development projects, as well as researchers and academics on safety issues in design.
The guide will be useful for those who want to embed good practice and address safety in their design. It should be used in tandem with local design guidance, and may be useful to draw attention in identifying where safety challenges may arise in a design or simply help identify gaps in the existing guidance. From that perspective, it may also be useful to those in LMICs who are about to update local guidance, or who are trying to adapt guidance from other countries to local conditions. The guide also provides information on tools that should be used as part of the design process to ensure that safety is embedded within projects and policies.
This guide gives good advice about how to include safety into road design, but it does not provide detailed information on how to design road projects. Road design standards vary across countries, with different approaches and dimensions used. The information in this guide will not allow a designer to design a roundabout, a roadside barrier, or a high-speed rural curve. This document does provide external references for this type of advice. Rather, the document will help identify safety-related issues that need attention through design of a roundabout, a roadside barrier, or a high-speed rural curve or similar facilities. It also provides information on tools that should be used as part of the design process to ensure that safety is embedded within projects and policies.
Road infrastructure design plays a vital role in road safety outcomes. Safe infrastructure supports other road safety pillars by encouraging appropriate road user behavior (such as appropriate speed and correct lane position) and by providing a forgiving road environment if things go wrong. Poorly designed road infrastructure can give rise to dangerous road user behavior. One of the key realizations of the Safe System approach is that drivers make mistakes and will continue to do so, even if we can reduce how often these occur. This road user error has long been recognized as a significant contributor to poor road safety outcomes. However, roads of any given speed can be designed to reduce the likelihood of crashes occurring, and there is very clear evidence that the severity of outcomes when crashes do occur is significantly influenced by the road design. As outlined in this guide, once a crash is inevitable, it is the road infrastructure that will have the strongest influence on the severity of the crash outcome. By providing a forgiving road design, we can substantially reduce serious crash outcomes Even if a crash still occurs, improved road infrastructure can save many lives and prevent debilitating injuries.
Road users will continue to make errors, no matter how well trained, and these errors will lead to crashes. The Safe System approach to road safety makes clear that road users should not be penalized with death or serious injury when an error does occur. Therefore, the road system needs to take account of this human error and ensure that a forgiving road system is provided that help prevents severe crash outcomes. Fundamental to this Safe System is a shared responsibility to address road safety. This means that road managers and designers have a significant responsibility to provide a road system that protects all road users. This can be achieved through appropriate designs of roads as outlined in this guide.
The following 8 Safe System principles are recommended to ensure safety in sustainable road transport system design:
Inclusiveness: Road design needs to be for all road users—not only for motorized vehicles.
Road functionality: Roads serve two functions: “access and mobility” or “movement and place.”
Clarity: Design should meet road users’ expectations and be free from any surprise to road users.
Homogeneity: Design should limit differences in vehicle speed, direction of travel, mass, and size.
Safe Speed: Design should support Safe System speeds.
Forgiving roads and roadsides: Roads and roadsides should be forgiving, i.e., free from hazards.
Minimized exposure: Design needs to minimize exposure to risk for all users.
System design: Road design should be done in a way to support other elements of the Safe System.
Each is explained in further detail in this guide.
Road design based on guidelines and standards will not necessarily produce safe outcomes. This has unfortunately proven to be true in many situations given that projects built using guidelines and standards still result in death and serious injury. Because of the complexities of road design, additional checks and tools are required to help identify safety risk and maximize the safety potential through design. Relevant tools include road safety audit/inspection, road infrastructure safety assessments (including international Road Assessment Program (iRAP)), and Safe System assessment. In addition, application of relevant safety metrics in project planning and design is required to set appropriate safety targets and track our progress towards such targets. These tools and processes are discussed further in this guide.
GRSF in Action
Since its inception in 2006, the GRSF has received total donor pledges of $74 million, in addition to unquantified support from the World Bank in its hosting capacity. GRSF work has expanded to 84 countries, improving road safety outcomes through technical assistance, training and capacity building, and grant-funded activities.
GRSF plays a key role in global road safety research, leadership, advocacy, guidance, and delivery by participating in numerous influential initiatives. Some highlights of the GRSF impact are:
- $2.68 billion
worth of World Bank investment projects supported by GRSF grants in FY21
- 10,500 lives
saved through GRSF Grants and World Bank loans since 2016
- ~35,000 km
of roads surveyed & assessed for road safety under the GRSF – Bloomberg Program since 2010
- ~10,000 km
of roads where safety recommendations were incorporated into designs under BIGRS since 2010
- 14,000professionals trained
under BIGRS since 2010, in learning activities led by GRSF or where GRSF contributed
of the FY21 Call for Proposals has gone to support external partners, up from 53 percent in FY20
by GRSF, resulting in 7 grants on road safety research, advisory and capacity building in FY21
GRSF presentations, workshops and events hosted/arranged for road safety in FY21
reports, blogs, and other knowledge products published by GRSF in FY21