Beck and teammates investigated how close cars are to bicycles being passed and their findings have implications for the design of not only roadways but also generally, for hallways within buildings, for example. The Beck-lead team found that when “Participants had a custom device installed on their bicycle and rode as per their usual cycling for one to two weeks. . . . on-road bicycle lanes and parked cars reduced passing distance [the distance cars were from the bicycles].” A press release issued by Monash University (available at https://www.monash.edu/news/articles/more-than-a-stripe-of-paint-needed-...) provides additional details: “marked on-road bicycle lanes and parked cars reduced the distance that motorists provide when passing cyclists. . . . ‘When the cyclist and driver share a lane, the driver is required to perform an overtaking manoeuvre. This is in contrast to roads with a marked bicycle lane, where the driver is not required to overtake. This suggests that there less of a conscious requirement for drivers to provide additional passing distance.’ [Quote attributed to Beck.] Dr. Beck said in order to improve safety and increase cycling participation, it is clear that far greater investment is needed in providing infrastructure that separates cyclists from motor vehicles by a physical barrier.” So, in summary, it seems that when bicycles are in a separate, marked lane, drivers do not maintain as great a distance from them as they do when the car drivers and bicyclists are in the same lane and the car drivers need to maneuver around the bicyclists to pass them.
Ben Beck, Derek Chong, Jake Olivier, Monica Perkins, Anthony Tsay, Adam Rushford, Lingxiao Li, Peter Cameron, Richard Fry, and Marilyn Johnson. “How Much Space Do Drivers Provide When Passing Cyclists? Understanding the Impact of Motor Vehicle and Infrastructure Characteristics on Passing Distance.” Accident Analysis and Prevention, in press, https://doi.org/10.1016/j.aap/2019.03.007