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More than 1.2 million people die on roads around the world every year. That is equivalent to roughly one person dying every 30 seconds, or over 3,400 people dying every single day of the year.1 Many of these deaths occur on urban roads and are preventable crashes caused by behavior induced by street design.
Creating safe streets is a critical responsibility shared by designers, engineers, regulators, and civic leaders. Even in the cities with the best safety records, the threat of traffic violence makes movement around the city a potentially dangerous daily activity. Highway-like street designs that prioritize automobiles over vulnerable users and encourage high speeds fail to provide safe environments.
A New Paradigm for Safety
The new paradigm for safety is built on human limits. The human body is fragile and can only survive certain forces. This means:
When vehicles move at or below 40 km/h, potential conflicts take place at lower speeds, dramatically increasing the chances of survival in the case of a crash.
Studies from around the globe have shown that most traffic deaths, especially the easily preventable pedestrian deaths, occur on a small percentage of arterial streets.2 These streets are rendered dangerous by design. They contain the following characteristics:
The combination of high traffic speeds and volumes, long crossings, and large distances between marked crossings make them fatal corridors for vulnerable users.
The relationship between impact speed and risk of pedestrian death.
Several recent studies (Pasanen 1993, DETR 1998, Rosen and Sanders 2009, and Tefft 2011) show the existence of a clear relationship between vehicular speeds and pedestrian casualties, supporting the idea that speeds over 40 km/h should not be permitted in urban streets. However, most of these studies were conducted in high-income countries and there are reasons to believe this relationship might be even more extreme in low- and middle-income countries.3
The relationship between speed and stopping distance. The graphic above depicts minimum stopping distances, including perception, reaction, and braking times. They are based on dry conditions and assume perfect visibility.4
Common Causes of Traffic Fatalities
Many traffic injuries are directly related to design. Conditions become more dangerous with the addition of speed. Common causes for traffic fatalities include the following:
Safe Design Supports Education and Enforcement
Regulations and education are critical to creating a culture of safety. However, a street cannot be made safe if it has been designed to prevent people from making safe decisions. Most road safety agendas focus on reducing probability of human error through education and enforcement, without emphasizing the design of safe streets. Design can ensure that a crash or conflict caused by human error will be limited in its severity. The design of a street is often far outside the scope of a safety project, but it can have direct and indirect impact on the safety
of street users.
Vision Zero and Sustainable Safety Programs
The Vision Zero (initiated in Sweden) and Sustainable Safety (initiated in the Netherlands) programs are proactive safety programs being adopted by an increasing number of cities around the world. The premise of such programs is that loss of life is unacceptable, and their goal is preventing all serious road crashes. These initiatives place the burden of safety on the system design, not the road user. Innovative street designs that reduce speed, strict enforcement against traffic violations, legislative ordinances that lower speed limits, and public awareness campaigns have proven to be impactful strategies adopted by these programs.
1. World Health Organization, Road Traffic Injuries (Geneva: WHO, 2015).
2. World Health Organization, Global status report on road safety (Geneva: WHO, 2015), 9.
3. Ben Welle et al. Cities Safer by Design: Guidance and Examples to Promote Traffic Safety through Urban and Street Design (Washington, DC: World Resource Institute, 2015). Erik Rosén and Ulrich Sander, “Pedestrian fatality risk as a function of car impact speed,” Accident Analysis and Prevention 41, No. 3 (2009).
4. “Stopping distances,” Department of Transport and Main Roads, Government of Queensland, accessed June 7, 2016, http://www.tmr.qld.gov.au/Safety/Driver-guide/Speeding/Stopping-distances.aspx.
Adapted by Global Street Design Guide published by Island Press.
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