Bike lanes effect on motorist distance from cyclists when passing

From the Chicago Metropolitan Agency for Planning -- Most studies concerned with the influence of on-street bike lanes on safety rely on crash data for evaluation, but a study from researchers at the University of Waterloo examined the lateral separation (passing distance) between motorized vehicles and cyclists when the motorized vehicles were passing the cyclist.  The study, which primarily focused on four-lane urban arterials with/without exclusive bike lanes where the maximum posted speed limit was 50 km/h (31 mph), finds that roadways with exclusive bike lanes result in greater separation between bicyclists and motor vehicles, as compared to roads with no bike lanes. In addition, unsafe passing maneuvers (defined as passing distances of less than 1,000 mm, or 39 inches) were observed less frequently on the facilities where exclusive bike lanes were present.  Furthermore, when bike lanes were not present, a much higher proportion of vehicles passing cyclists move laterally (to their left) and encroach upon the adjacent lane, resulting in higher number of potential conflicts between motor vehicles on both two- and four-lane facilities. [Visit the website ...]

Properly designed bike lanes like this one on Glasgow Ave in Glasgow make an excellent case. At least for this photo, all vehicles are seen moving well away from the bicyclist, providing far more than the required 3' of passing space. 

Poster's notes:  Not sure what the results would be here, where bike lanes are commonly found on arterial roads with speed limits in the 45-50 mph range.

Bike lanes can be controversial because many are poorly designed and fail to consider bicyclist's needs as participants in vehicular traffic. Often times, however, the opposite is true. Many bike lane treatments - like the above in Glasgow - are properly designed and find support among a large majority of Delaware bicyclists.

One example of an improperly designed bike lane is found on Red Lion Road/Route 71. If it was striped this way for cars, the solid white line would guide them into the woods.