Likely not as many (most?) sidewalks aren't officially open to bikes (Regardless of enforcement on the one hand and regardless of some people preferring to use them on the other).
I remember as a 12 year old a cop swore at me and told me he was going to take my bike if he saw me ride on the sidewalk again. So then 2 blocks later ANOTHER cop is swearing at me calling me crazy and going to drive me home for riding on the road when there was a sidewalk to ride on. I laughed and said the other one told me to get off the sidewalk. He called him and they got in an argument and hung up on him. I just rode my bike on the sidewalk.
Heh, that's awesome. I think it illustrates how confused people are in general about where bikes are supposed to be, which I think is a complicated cross of law, culture, cycling ability, and infrastructure.
The police have never hassled me for being on any road on a bike. But man, do the dudes in pickup trucks with truck nuts love to tell me to get off the road.
Within the downtown area of Washington, DC, bikes are not allowed on the sidewalk. (This is roughly the area bounded by Massachusetts or Florida Ave. on the north, Georgetown on the west and the Capitol on the east.) Couriers, tourists, and a lot of others disregard the regulation.
It really varies by the city. Some prohibit bikes on sidewalks, others allow them at least in some areas, and some only allow children under a certain age. There's no consistency.
