Guides & Manuals

Speed is one of the main road safety risk factors and is universally recognized as the leading contributor to road fatalities and serious injuries. But there is good news: the speed problem is solvable. Interventions that are proven to be effective exist, and it is well understood where and how they should be applied.

The newly published “Guide for Safe Speeds: Managing Traffic Speeds to Save Lives and Improve Livability” outlines interventions that work and provides guidance on how to select and implement speed limits that are safe for all road users. It also explains how barriers to changing traffic speeds—which are often based on lack of knowledge or misunderstandings—can be overcome.

A primary feature of the guide is its comprehensiveness. The guide covers all types of roads—from city streets to inter-urban roads and motorways (existing or new); all types of road users—from vulnerable road users such as pedestrians and cyclists to heavy motorized traffic; all types of speed limit changes—from national general speed limits to localized changes based on risk factors; all types of challenging constraints—from lack of resources to lack of data; and all types of countries—from low-income to high-income.

Road traffic crashes result in an estimated 1.35 million deaths and 50 million injuries worldwide per year with over 90 percent of these occurring in Low-Middle Income Countries (LMICs). Aside from the obvious pain and suffering this inflicts on individuals and communities, these deaths and injuries also place a large financial burden particularly on LMICs, by slowing economic growth.  

The scale of the current response to this continuing crisis does not match the size of the problem. In addition, limited road safety resources are often expended on ineffective or suboptimal interventions. While road safety knowledge has improved over recent decades, there is still a need to improve decision making when selecting and applying effective evidence-based road safety interventions. Effective interventions are those that reduce fatal and serious injuries.

The World Bank's Global Road Safety Facility (GRSF) has developed this evidence-based guide on “What Works and What Does Not Work” in road safety in response to the critical need for effective evidence-based solutions.

This guide has been prepared to help readers understand that not all road safety interventions are equally effective and that what appear to be “common-sense” approaches to selecting road safety interventions will often not be the best.  Although some provide benefits, others have very limited or even negative impacts, despite being commonly—and mistakenly—recommended or accepted. The guide offers a range of recommendations with a focus on interventions in LMICs, although the information may also be of relevance to all countries. The contents will be valuable to those working on road safety at policy or practitioner levels, including World Bank technical team leaders and others who seek to establish, expand, or improve road safety programs in LMICs.

The guide sets knowledge on evidence-based interventions within a “Safe System” context, providing advice on each of the Safe System pillars (road safety management, safe roads, safe speeds, safe vehicles, safe road users, and post-crash care) while recognizing that evidence-based solutions must be drawn from across pillars to produce effective road safety outcomes. At the core of this document is a summary table with an overview of beneficial and non-beneficial interventions based on sound scientific evidence. This is followed by more detailed information including case studies and references to the evidence base to support the summary.

Many safe road interventions are recommended for adoption, including integrated public transport, roadside and central barrier systems, medians, infrastructure to support appropriate operational speed for road users, roundabouts, grade separation and interventions to reduce exposure to risk at intersections, pedestrian footpaths and crossings, separated bicycle and motorcycle facilities, and traffic signs and line marking (including audio-tactile line marking). Some of these are highly effective, with up to a 70 or 80 percent reduction in fatalities and severe injuries (for example, safety barriers and roundabouts).

Various speed-related interventions also produce significant benefits, with some able to almost eliminate death and serious injury. Examples of effective speed interventions include traffic calming (including humps and chicanes), roundabouts, raised intersections and crossings, gateway treatments, lower speed limits (including 30 km/h (20 mph) zones for pedestrians) and speed cameras.

A variety of road user-based interventions have been implemented over many years, with effective examples including extensive supervised on-road practice and/or graduated licensing systems as part of the driver-licensing system, increased age for driving license eligibility, hazard perception training and testing, public education and campaigns as part of an integrated strategy (especially communicating enforcement to increase general deterrence), enforcement, penalties, alcohol interlocks, fatigue and speed monitoring, and increased helmet wearing rates.

Key vehicle-based interventions include applying minimum vehicle safety standards and vehicle ratings (through the Global New Car Assessment Program, or “NCAP”), seat belts, periodic vehicle maintenance, daytime running lights, under-run guards on trucks, Electronic Stability Control, and other advanced vehicle technologies.

Enhanced post-crash care can also produce better road safety outcomes, including systems to improve emergency response time, better emergency care, improved first aid skills for the public, and improved hospital care.

Equally important, the report also identifies clear examples where interventions are not effective. The worst of these are interventions that increase risk. These include increasing travel speed without improving quality of safety infrastructure, most forms of post-license driver and rider education and training, and many (but not all) forms of regular school-based driver education (such as those that seek to increase car-handling skills). The increase in risk is typically because such initiatives increase the level of confidence leading to an increase in risk taking. Other interventions that have no demonstrated safety benefits are to be avoided. These include license schemes through application or payment, training programs or education within schools that aim to improve road safety knowledge (including ad hoc visits by road safety experts or enthusiasts), and education campaigns conducted in isolation.

There are effective alternative interventions for each of these as described within this document, and these should be applied instead. It is extremely important that resources are not wasted on ineffective interventions on behalf of road safety but rather that evidence-based road safety interventions are employed.

There are a variety of documents available on the issue of road safety intervention effectiveness, many of which are referenced here. However, there are some key points of differences and added value in this guide, including a synthesis of the evidence on a broad range of interventions and a contrast between effective and noneffective interventions, allowing readers to compare options. Where noneffective interventions are identified, viable effective interventions are provided thereby supporting decision making. The guide also provides direct advice to those working in LMICs, drawing on key sources of information where this is available. Importantly, concise yet robust evidence is provided across each of the Safe System pillars.

There is a need to continue building the knowledge base on effective road safety interventions, particularly in LMICs where there are a number of gaps in knowledge. The contents of this guide represent a useful, up-to-date summary of current knowledge for application.

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In many countries around the world, deficiencies in data or data quality impair evidence-based road safety policy making. While many countries collect road safety data, the collection is not necessarily comprehensive. Further, many countries can be unaware of data gaps in their system, which prevents them from soundly analyzing their road safety problems. Therefore, road safety data definitions and collection methods must converge into standard international criteria, thus allowing for comparisons in space - across countries - and in time.

This is the raison d’etre of regional road safety observatories, which have been developed, for example, in Latin America (OISEVI), Africa (ARSO), and Asia-Pacific (APRSO). They present an opportunity for joint regional efforts to improve, in a harmonized way, road safety data collection and analysis. Regional road safety observatories promote the adoption of a common set of road safety indicators based on common definitions and serve as an avenue to assist countries in improving the management of their crash data systems.

This document is designed to support reviewers in the assessment of road safety data collection; the complete range of safety data should be considered. This task can be complicated because collection of road safety data is often not achieved by activities dedicated to this purpose, but rather through piggybacks on other sources. For example, activity reports from police or hospitals are used to provide material for legal or medical purposes. The routines involved frequently have a long history in which gathering reliable and complete statistics has had secondary priority, at best. The various actors involved reflect the complex structure of a country’s judicial and executive system, which, generally, are not coordinated. Consequently, any review of the data collection process requires some “detective work.”

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.