While in rare instances this type of facility may be necessary, or desirable for use by small children, in most cases it should be avoided. Cyclists are safer when they are allowed to function as roadway vehicle operators, rather than as pedestrians. In some urban situations, preference may be given to accommodating pedestrians. Sidewalks should not be signed for bicycle use - the choice should be left to the users. At night, the curbs cast shadows on the lane, reducing the bicyclist's visibility of the surface.
Extruded curbs make bikeways difficult to maintain and tend to collect debris.
They are often hit by motor vehicles, causing them to break up and scatter loose pieces onto the surface. These can deflect a bicycle wheel, causing the cyclist to lose control. If pavement markers are needed for motorists, they should be installed on the motorist's side of the stripe, and have a beveled front edge. This creates a dangerous condition for bicyclists. Shoulder widening on one side C.5.