To minimize inhalation of air pollution while walking and cycling and still reaping the benefits of exercising, UBC researches say cyclist should be riding at speeds between 12 to 20 km/h, while pedestrians should be walking at two to six km/h. “The faster you move, the harder you breathe and the more pollution you could potentially inhale, but you also are exposed to traffic for a shorter period of time. This analysis shows where the sweet spot is,” said Alex Bigazzi, a UBC transportation expert in the department of civil engineering and school of community and regional planning who conducted this analysis.
Using a US Census-based computer model of 10,000 people, Bigazzi calculated ideal travel speeds, called the minimum-dose speeds (MDS) for different age and sex groups. The ideal speed linked to the least pollution risk for female and male cyclists under 20, on a flat road was calculated to be at 12.5 and 13.3 kilometres per hour, respectively. For pedestrian in the same age group, a walking speed around 3 kilometres per hour was determined to be associated with least pollution risk. Their older counterparts on the other hand should aim at reaching at least four kilometres per hour in order to breath in the least amount of pollution over a distance. Ideal travel speeds for other road grades were also computed by Bigazzi. “If you move at much faster speeds than the MDS—say, cycling around 10 kilometres faster than the optimal range—your inhalation of air pollution is significantly higher,” said Bigazzi. “The good news is, the MDS numbers align pretty closely with how fast most people actually travel.” A recently published paper in the International Journal of Sustainable Transportation describes the findings from Bigazzi’s research on the amount of toxic chemicals absorbed by cyclist on busy street. More research is needed to further assess the minimum-dose speed estimates with on-road data.