One problem that decision-makers continue to face when deciding what type of bicycle facilities (if any) to invest in is that there just isn’t very good data available about the relative safety of different facility types. It would be great if we could say something like, “cyclists on trails are 50% less likely to be in a crash with a motor vehicle than a cyclist in a bike lane”, but we just can’t say that confidently. There have been a lot of studies that try to reach conclusions like this, but there are simply too many variables (primarily the riders themselves) to make any conclusive statements.
The most often-cited source comes from a study by William E. Moritz in 1998. The study is clearly dated, but it is convenient in that the results seem to present a simple message about where crashes are occurring. In fact, this is the source that even the MnDOT sponsored safety website Share The Road cites. Here are the results, as presented by Share The Road:
From Share The Road:
A 1996 [Ed. - the data was collected in 1996, the study was completed in 1998] study determined the likelihood of a bicycle accident by facility type. (This is the only major study that adjusts crash data for the number of miles bicyclists actually travel on these facilities.) The study found that riding on the road is not only safer—but much safer—than riding on these other types of facilities.
Bicyclists are 25 times more likely to experience an accident when riding on a sidewalk than riding on a major street—even one that neither has a designated bike lane nor is designated as a bike route. And bicyclists are twice as likely to experience an accident on a multi-use trail than on an unmarked street.
Bicyclists are discouraged from riding on the sidewalk. Not only is there potential for a collision with a pedestrian. More importantly, motorists are not expecting a bicyclist, moving much more quickly than a pedestrian, to cross the street in a crosswalk. So, motorists often fail to detect bicyclists on sidewalks and strike the bicyclist in the crosswalk.
However, it’s important to keep in mind the methodology of the study. Moritz’ data is self-reported survey answers about crash incidents and miles traveled on each facility type from members of the League of American Bicyclists – hardly a population representative of cyclists generally (especially in urban areas), and self-reporting distances is problematic as well.
Moritz data may be true for some cyclists some of the time, but we can’t make broad statements about bike safety based on this or similar studies. In any given corridor, there are enough variables (most notably among the cyclists themselves), that this study, and most other similar studies, aren’t particularly useful in making a recommendation about which type of facility will minimize the risk of crashes. This isn’t to say that there aren’t known safety issues related to, say, cycling on sidewalks in urban areas, or that there aren’t other studies beginning to fill this gap, but additional study is needed before we can confidently cite any specific safety statistics.