Cycling & Traffic Corridors: Health Risks & Benefits

Within the public health sector, there can be an uneasiness about encouraging people to cycle along busy traffic corridors. While most public health professionals appreciate that health benefits can be associated with the physical activity involved in cycling, it has not been clear how those benefits compare against the health risks associated with air pollution and vehicle-related collisions along busy traffic corridors. A new study, which compared the health risks and benefits of cycling in an urban area, found that the health benefits far outweigh the health risks.

This study was conducted in Barcelona, Spain, where a new public bicycle sharing initiative, called Bicing, has been introduced to increase active transportation in that city. The researchers used all cause mortality as the indicator for health impacts. They compared the health risks presented by air pollution and vehicle-related collisions for cyclists, against the health benefits associated with the increase in physical activity among cyclists They also estimated the reduction in greenhouse gas emissions.

Barcelona’s Bicing program, which was introduced in 2007, had 182,062 subscribers by 2009 (11% of the City’s population). The study team calculated that 28,251 members used the Bicing scheme on a regular basis and assumed that 90% of those members were new cyclists. To estimate mortality from exposure to air pollution, the researchers used fine particulate matter as the indicator pollutant and data from exposure studies directed at cars and bicycles in Barcelona. To estimate mortality from vehicle-related collisions, they used the mortalities per billion kilometres travelled by bicycle and car from data collected over the previous nine years. To estimate the
health benefits of physical activity, they used the relative risks of all cause mortality for commuters who use bicycles compared with other modes of transportation from a study in Copenhagen. They estimated the reduction in greenhouse gases using emission factors from the Catalan Office of Climate Change and calibrating them for the Barcelona fleet of vehicles.

The researchers estimated that, when Barcelona residents who travel by bicycle were compared to those who travel by car, the relative risk for all cause mortality associated with:

the increase in physical activity would be 0.80, resulting in 12.46 avoided deaths among Bicing members each year;
the increased exposure to fine particulate matter was 1.02, resulting in 0.13
additional deaths among Bicing members each year; and
the increase in vehicle-related collisions was 1.0007, resulting in 0.03 additional deaths among Bicing members each year.

The research team estimated that the Bicing initiative is reducing the number of deaths among Bicing members in Barcelona from 52.15 to 39.87 each year. They also estimated that the Bicing initiative is reducing carbon dioxide emissions (i.e. greenhouse gases) by 9,062 metric tonnes per year.

These results suggest that the health benefits associated with cycling along busy traffic corridors outweigh the health risks, albeit in a European context. They also suggest that significant health benefits can be associated with a relatively inexpensive initiative such as Bicing.

Note: In a North American context, it is possible that the health risks associated with vehicle-related collisions are greater than those estimated for this study because we do not have the infrastructure (e.g. bike lanes), volume of cyclists, or awareness of cyclists that exists in European countries.

Rojas-Rueda, David, Audrey de Nazelle, Marko Tainio, Mark J Nieuwenhuijsen. “The health risks and benefits of cycling in urban environments compared with car use: health impact assessment study”. BMJ 2011; 343:d4521 doi: 10.1136/bmj.d4521

Prepared by Kim Perrotta