Traffic injuries much more common in poor areas, study finds

Here’s another way that rich people are different – they experience far fewer traffic accidents in their neighborhoods, according to a new study.

This isn’t exactly a shocking conclusion. There are an estimated 40,000 road deaths in the U.S. each year, and many studies have found that these are more likely to involve low-income people in low-income areas.

But there’s nothing about being poor that should make a person inherently more vulnerable to being hurt in a car crash. As researchers from Montreal explained in their study, “deaths and injuries result from the transfer of a motor vehicle’s kinetic energy at a rate that exceeds the human body’s protective capacity.”

So what is it about poor neighborhoods that explains the heightened risk? To find out, the researchers gathered information on all road traffic injuries on the Island of Montreal between 1999 and 2003. (The island is served by a single ambulance company, which provided records for the study.) The researchers focused on 19,568 accident victims who got hurt at 17,498 intersections, all of which were located in census tracts with at least some residents. Intersections that straddled multiple census tracts, were adjacent to highway on-ramps or were in purely industrial or commercial areas were not included in the analysis.

Then the researchers took all of those intersections and sorted them into five categories based on the average household income for the census tract in which they were located. The main comparisons were between the 20% of intersections in the poorest census tracts and the 20% of intersections in the wealthiest census tracts. Here’s some of what they found:

* Population density in the poorest census tracts was 2.7 times higher than in the wealthiest census tracts.

* Average traffic at intersections in the poorest neighborhoods was 2.4 times greater than in the richest neighborhoods.

* 30% of the intersections in the poorest neighborhoods included a major traffic artery, compared with only 11.5% of intersections in the richest neighborhoods.

* The number of four-way intersections in the poorest census tracts was nearly twice as high as in the wealthiest census tracts. Collisions involving injuries are more common at four-way intersections than at three-way intersections.

The net effect of these (and other) factors was not good for motorists, cyclists or pedestrians in the lowest-income areas. The researchers found that the number of pedestrians injured in the poorest census tracts was 6.3 times higher than in the richest census tracts. People riding in cars were also more vulnerable in the poorest areas – the number of injured motor vehicle occupants was 4.3 times greater in poor areas than in rich ones. The story was similar for cyclists – the number of injuries was 3.9 times higher in poor areas than in rich ones.

The researchers calculated that for every 1,000 additional vehicles that pass through an intersection each day, the number of people injured in cars rose by 7%, the number of injured pedestrians rose by 6%, and the number of injured cyclist rose by 5%. Since poorer neighborhoods had more traffic, they also had more injuries.

“We found that environmental factors associated with a greater risk of crashes” – the number of people exposed to crashes, the total volume of traffic, and the geometry of roads and intersections – “were more frequent in the poorest neighborhoods,” the study authors wrote. These three factors accounted for “a substantial portion” of the difference between the poorest versus the richest neighborhoods, they added.

“It should be underscored that poverty per se does not produce RTIs [road traffic injuries] – exposure to moving vehicles does,” they wrote.

The results were published online Thursday by the American Journal of Public Health. The full study is behind a pay wall, but you can read an abstract here.

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