I'm looking to get a road bike...if I can reach speeds up to 40km/hr, than i'll be on the road and take the entire lane. But until then, I can't really go that fast on my mountain bike.
See, this is why I stay on the sidewalk for quite a bit on my commute. I ride a cheapie folding bike which has a top speed of 7mph on flats, and around 15-17mph on steep downhills. I don't bother riding it on hills--I can jog it up faster (around 4-5mph). Of course, the engine needs some work, but from what I hear, even uber-fit riders have trouble going past 15mph on flats, as the gearing is so ridiculously low. I do NOT want to ride in traffic going 50mph when I'm going 7mph. It's like a death wish.