Study: More cyclists leads to fewer collisions


Having ridden the crowded and chaotic cyclepaths of Europe, it’s hard to imagine how having more and more cyclists could lead to fewer collisions, but that’s exactly what a recent study conducted by the University of Colorado at Boulder found.

Boulder has one of the highest rates of cycling in the country, measured at 12 percent of the population. The proximity of the campus made it an ideal research location.

The researchers wanted to create safety performance functions (SPFs) for bicycles in Boulder. SPFs model the mathematical relationship between the frequency of crashes and major factors related to them. Yet while there are SPFs for vehicles, there are none for bikes.

The authors created their SPF for Boulder by studying crashes at intersections throughout the city where more than two-thirds of collisions occur. They compared the crash data to bicycle count data.

The researchers found that the chance of collision decreased with more bicyclists.

The risk of accident was relatively high at intersections with less than 200 bicyclists per day.

The reasons for this remain unknown.

“Other studies have hypothesized that when drivers expect to see a significant number of bicyclists on the street, their behavior changes,” said study co-author Wesley Marshall, PhD, PE, assistant professor of civil engineering at CU Denver’s College of Engineering and Applied Science. “They are more likely to look over their shoulder for a bicyclist before taking a right turn.”

Cyclists may also be attracted to safer areas.

“But we think there is even more to the story and we’ll be looking for that in our next study,” said Marshall.

The study was co-authored by CU Denver’s Bruce Janson, PhD, professor of civil engineering and Krista Nordback, PhD, PE. It was published last month in the journal Accident Analysis & Prevention.


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