if we're talking about from a transport perspective, it really varries.

Downtown LA I'm consistantly as fast as cars. They drive a little faster, and I catch them at stoplights.

In the burbs where I live, cars routinely travel at 50+ and I do about 10-15 mph.

however, if we're talking about saftey and impact issues, I think the mass of a car has some added "weight" here. (sorry, couldn't help myself)

-- James