Saving Lives with Smart Urban Design

Cities Safer by Design, a report by the World Resources Institute
Cities Safer by Design, a report by the World Resources Institute / WRI

Globally, 1.24 million people are killed in traffic accidents every year, with more than 90 percent of these deaths occurring in low and middle-income countries. Traffic-related incidents are the eighth-leading cause of death worldwide, and the number-one leading cause of death for those between the ages of 15-29. A response to the United Nations’ declaration to create a “Decade of Action” on improving traffic safety, Cities Safer by Design, a new report by the World Resources Institute (WRI) Ross Center for Sustainable Cities, offers urban design best practices and real-world case studies both developed and developing world cities can use to put an end to traffic deaths and injuries.

Cities Safer by Design presents five basic urban design elements that create safer travel environments: block size, connectivity, lane width, access, and population density.

Block Size

Safe urban design is about reducing motor vehicle speeds. The faster a driver goes, the more difficult it is for him or her to avoid hitting a pedestrian in their path. Due to less frequent interruptions, larger blocks allow vehicles to accelerate more freely. More junctions mean more places where cars must stop and pedestrians can cross. According to the report, to improve safety and walkability, blocks should be 75-150 meters long. If blocks are any larger than 200 meters, mid-block pass-throughs with signals or raised crossings should be added every 100-150 meters.

Smaller block sizes have been successfully implemented in central areas of Shanghai, such as Xin Tian Di, to create more walkable neighborhoods. More Chinese cities that had mistakenly built “super blocks” are starting to apply the same approach.

shanghai 2
A street for pedestrians in Shanghai / Jamie Sinz

Connectivity

The report recommends increasing connectivity to multiples modes of transit in order to decrease travel distances and improve access to destinations. Creating multiple routes for pedestrians and cyclists also helps disperse traffic, discourage car use, and reduce travel time.

Mexico City has also created walkable urban landscapes around its Metrobús bus rapid transit (BRT) system that enables safe bicycle and pedestrian access.

Bikers and BRT passengers outside of the Mexico City Metrobus / EMBARQ by  Alejandro Luna
Bikers and BRT passengers outside of the Mexico City Metrobus / EMBARQ by Alejandro Luna

Vehicle Lane Width

The amount of a street devoted to vehicles shapes the amount of street available for pedestrian crossings, bike lanes, parking lanes, and landscape curb extensions. Reducing street widths creates a safer pedestrian experience because they shorten pedestrian crossing distance and exposure to cars and also slow traffic by “increasing drivers’ perception of impediments.” Again, slower traffic mitigates the potential severity of crashes.

According to the report, evidence from Mexico City shows that as the maximum pedestrian crossing distance at an intersection increases by 1 meter, the frequency of pedestrian crashes increase by up to 3 percent. Other studies highlighted in the report show the most significant relationship to injury crashes is street width and street curvature. As street width widens, crashes per mile per year increase exponentially.

Access to Destinations

Neighborhoods should be designed to include transit, parks, schools, and stores within walking distance, which is defined as 0.5-kilometers. Having a variety of destinations in neighborhood clusters encourages people to meet close to home, decreasing the need for vehicular travel and improving overall safety.

In the Coyoacan neighborhood of Mexico City, the prevalence of shops and public spaces encourage walking while discouraging vehicular traffic. Recalling an earlier area before sprawl took over the city, Coyoacan’s cobbled streets lead to garden plazas where street vendors gather.

Santa Catalina Plaza and Church located on Avenida Sosa in the Coyoacan borough of Mexico City / Thelmadatter
Santa Catalina Plaza and Church located on Avenida Sosa in the Coyoacan borough of Mexico City / Thelmadatter

Population Density

A 2009 study cited in the report found that for an increase in density of 100 persons per square mile, there was a 6 percent reduction in injurious crashes and a 5 percent reduction in all crashes after controlling for vehicle miles traveled, street connectivity, and land use. In contrast to more sprawling cities, high-density cities not only reduce the need for vehicle travel, but also reduce the need for their associated infrastructure, such as roads and sewers.

Tokyo has successfully developed high-density mixed-use neighborhoods near rail and bus stations. According to the report, Tokyo has a traffic fatality rate of 1.3 per 100,000 residents. Compare this rate to Atlanta, Georgia, one of the most sprawled-out cities in the U.S., which has 9.7 traffic fatalities per 100,000 residents.

Street in Jiyugaoka,Tokyo
Street in Jiyugaoka, Tokyo / Cozyroom_mimi (Flickr)

With the percentage of the world’s population living in cities expected to hit 70 percent by 2030, reducing traffic fatalities from unsafe streets should be a priority. Safer streets also increase the quality of life for urbanites, particularly for those in developing countries. WRI’s report shows policymakers, urban designers and planners, and landscape architects what works: designing for pedestrian safety means improving urban health and sustainability overall.

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