When you are riding your bike on a roadway, you are riding parallel to other traffic, conforming to rules of the road that provide for the smooth movement of traffic and the management of conflicts.  You are moving in a position that other roadway users expect to find a vehicle.

When you are riding on a sidewalk, you frequently are also riding in a roadway.  This occurs every time you cross an  intersecting street or driveway, where you will be travelling perpendicular (!) to the traffic on that roadway.  If you are riding at pedestrian speeds, you have plenty of time to spot approaching vehicles and yield if necessary.  But at cycling speeds that you would use if you actually want to get somewhere, you often will “appear” in these intersections as if by magic (that is what the driver that hits you will tell the officer).

Numerous studies (for example, see http://www.bikexprt.com/bikepol/facil/sidepath/sidecrash.htm and http://www.bicyclinglife.com/Library/Moritz2.htm ) have shown that crash rates for cyclists on sidewalks are considerably higher than for cyclists on roadways.

Roger Pierce