Bike Lanes Help Motorists Be Safe

CC BY-SA 2.0. Richard Masoner

This study provides shocking statistics on unsafe motorist behavior, but aims to give urban planners new tools for safer shared roads

Bruce Hellinga, a civil and environmental engineering professor at the University of Waterloo, cycles to work. Hellinga observes,

"I got frustrated by what I perceived as vehicles getting too close to me. You feel very vulnerable when a vehicle comes within what feels like mere centimeters."

So, in collaboration with graduate student Kushal Mehta and former postdoctoral fellow Babak Mehran, Hellinga set out to do something about his frustrations. The team outfitted bicycles with sensors and a handlebar camera as researchers cycled hundreds of kilometers in Kitchener-Waterloo, Ontario. The resulting statistics are shocking:

  • Twelve percent of motorists come within one meter (3.3. feet) of a cyclist on two-lane roads without bike lanes;
  • Six percent of motorists violate that often legally established 1-m 'safe space' even on four-lane roads.

With bike lanes, those numbers drop significantly:

  • On two-lane roads, unsafe passing instances drop from 12% to 0.2%
  • On four-lane roads, unsafe passes drop from 6% to 0.5%

In short, the study proves that bike lanes "virtually eliminate" motorists squeezing into cyclists' space. Hellinga's hypothesis is that "drivers aren't trying to scare cyclists or be inconsiderate. In many cases, they just don't feel they can leave more space because of the geometry of the road and the proximity of other vehicles."

But the purpose of the exercise isn't just to know how bad bikes have it. The team has developed a tool to help urban planners target the areas to prioritize for bike lane planning, in order to best reduce the number of unsafe situations, which is the primary goal of accident prevention theory.

The model uses bicycle demand, section length, annual average daily traffic (AADT), speed limit, and upstream traffic signal configurations as input parameters. Users of the tool can input their own "critical passing distance," using more or less than 1 meter according to the local regulations or custom. The model then predicts the expected number of unsafe passing events, allowing planners to justify an improved cycling infrastructure.

Safer cycling infrastructure encourages citizens to add bikes to their transportation options, which is good for human health and the environment.

The study is published in the March 2019 edition of the journal Accident Analysis & Prevention: A methodology to estimate the number of unsafe vehicle-cyclist passing events on urban arterials