A second thing to consider about bike lanes, in addition to keeping them clean, is to provide adequate width.Originally Posted by LittleBigMan
I read the AASHTO standards for bike lanes, and it appears that the outer bike lane stripe should be 5 feet from the curb, if the longitudinal joint between a 1 to 2 foot gutter pan and the road is smooth (where there is a curb and no on-street parking allowed.) The gutter pan is not to be included as part of the usable space. A minimum of 3 feet of resulting usable space is recommended. But if the joint between the gutter pan and the road is not smooth, a minimum of 4 feet of usable space is recommended.
Consider that a bicycle can be about 2 feet wide, and that overtaking traffic should allow 3 feet of passing space. Even riding nearest the right edge of the pavement (not safe or practicable,) a cyclist would need 5 feet from the road edge, not including the gutter pan.
As it is, these narrow designs force the cyclist to ride near the outside line of the bike lane. If debris is present, the usable space becomes almost negligible inside a 3 or 4 foot-wide bike lane. If a bike lane is to be similar to other traffic lanes, there should be some leeway on either side of the vehicle in the lane, especially in the case of a cyclist, who lacks the external safety protections that motorists enjoy.
To provide adequate usable space on the road for a cyclist in a bike lane, even assuming only 2 feet of leeway on either side of the cyclist, a bike lane would have to provide a minimum of 6 feet of usable space, double the AASHTO standard. This simple calculation does not even take into account road debris in the bike lane, but it assumes regular sweeping, as was discussed in the previously mentioned thread.