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Surrey study investigates effect of group cycling on exposure to pollutants

In an open access paper in the Journal of Wind Engineering and Industrial Aerodynamics, researchers at the University of Surrey (UK) have investigated the effect of group riding on cyclists’ exposure to vehicle pollutants. For major cycle lanes cutting thorough many large cities, cars and bicycles share the same stretch of road without any significant mitigation strategy in place to shelter cyclists from the polluting vehicles traveling nearby, the researchers note.

The use of narrow cycle lanes adjacent to the traffic often forces riders into a group, or a line one behind the other depending on the cycle lane width—especially in congested areas during peak hours.

In these cases, the turbulent mixing can be highly localised rendering the pollutant dispersion extremely dependent on the unsteadiness in the flow field. This unsteadiness, often neglected in air quality models, can at times be a dominant contribution to the cyclist overall exposure levels. Therefore, this work investigates this aspect further by considering different riding configurations and monitoring the cyclists exposure to road traffic pollution.

—Schmeer et al.

The team carried out a series of experiments were carried out in Surrey’s Environmental Flow (EnFlo) wind tunnel with a 1:50 scale of a typical London street canyon to assess the exposure of four cyclists riding in a group to the emissions of polluting vehicles. Two cases were investigated: a vehicle driving in front of a line of cyclists and then adjacent to them (as if it were overtaking them).

With a vehicle in front of a cycling group and little wind movement, the findings confirm that pollutant exposure decreases the further the cyclist is from the vehicle. With more wind, riding towards the back of the group can be a good strategy to minimize exposure.

When the vehicle is adjacent to the cycling group, results show how exhaust fumes can be trapped by a complex aerodynamic field, making the front riding position the place with the least exposure despite its proximity with the vehicle.

Cycling is encouraged to reduce congestion on the roads, as well as traffic emissions, yet despite many encouraging health aspects of cycling, the exposure to and inhalation of vehicle pollutants is something not to be forgotten, especially when used as a regular alternative transport method.

The findings of these experiments highlight group cyclists needs to consider their routes and position within a group, especially when roads become busier and narrower.

—Joy Schmeer, Postgraduate Researcher at the University of Surrey and lead author


  • Joy Schmeer, Paul Hayden, Alan Robins, Prashant Kumar, Marco Placidi (2023) “Group riding: Cyclists exposure to road vehicle emissions in urban environments,” Journal of Wind Engineering and Industrial Aerodynamics, Volume 235 doi: 10.1016/j.jweia.2023.105333



A friend of mine died of cancer after cycling to work every day for decades in Los Angeles and Orange County. He never smoked and ate super healthy.
Thanks Firestone etc. for ruining the mass transit system we had, setting it back many decades.


It looks like what they are saying is, if the car is in front, stay further back.
If the car is beside you, try to get in front of the exhaust.
Both of these seem like common sense to me.
IN general, cycling will improve your health, especially if you have a desk bound job, unless you live in a really polluted city.

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