Investigating air pollution risks for pedestrians and cyclists

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Although active forms of travel such as bicycling and walking provide many health benefits, they may also increase travelers’ exposure to air pollution—especially in urban areas, where the air pollutants that drive health concerns are typically at their highest concentrations.

Hankey’s instrumented trailer measured the air at “breathing” height rather than at tailpipe level.

Hankey’s instrumented trailer measured the air at “breathing” height rather than at tailpipe level.

To investigate the exposure of cyclists and pedestrians to these pollutants in the City of Minneapolis, researchers from the U of M’s Department of Civil Engineering (CE) are developing a block-by-block analysis of air pollution levels. In a presentation at the 24th Annual CTS Transportation Research Conference on May 23, graduate student Steve Hankey explained how this information could ultimately be used to identify high-risk locations and shape decisions about new nonmotorized infrastructure. The project is funded by the U of M’s College of Science and Engineering and the Humphrey School of Public Affairs.

In summer 2012, Hankey collected particulate air pollution measurements in Minneapolis using an instrumented bicycle trailer as he rode around the city on three 20-mile routes. Each route captured different levels of traffic and air pollution, Hankey said, and included a wide variety of road types and surrounding land uses.

Preliminary findings suggest that air pollution levels are 1.5 to 2.3 times higher in on-road locations than on off-street trails and 2 to 3.5 times higher in the morning than in the afternoon. Results also indicate that air pollution concentrations are associated with street classification and traffic intensity.

Arterial streets with the most traffic had the highest air pollution levels, with lower concentrations on local roads and off-street trails. “If you can choose to bike on a local road that’s a block or two off an arterial collector, that would make a big difference in your exposure,” Hankey said.

The project’s next step is to tie the existing mobile measures to land-use variables so the data can be extrapolated to other parts of the city, Hankey said. The resulting model will show air pollution levels for every block in Minneapolis.

The researchers plan to use this model in conjunction with bicycle and pedestrian traffic volume data being collected by a team of researchers from the Humphrey School led by Professor Greg Lindsey. The combined model could be used to identify “hot spots” with both large volumes of pedestrian or bicycle traffic and high levels of air pollution, Hankey said.

This information could be used to develop mitigation strategies in high-risk locations and to make recommendations for the development of future infrastructure in areas with lower pollution concentrations.

“We’ll also release the air pollution estimates so people can integrate them into existing tools,” Hankey said. “For example, in [the bike route tool] Cyclopath, a user could choose a low air pollution route instead of the fastest route or shortest route.”