[jordonwii]

> we don't really need vehicles driving faster than 15 kph

Tangent: if you've read Left Hand of Darkness, this reminds of the Gethenians - despite being a reasonably advanced people, they never invented a means of transport that goes faster than about 25mph. There's a brief discussion in the book about this that I thought was kind of fun to read:

"Traffic is controlled, each vehicle or caravan being required to keep in constant radio touch with checkpoints along the way. It all moves along, however crowded, quite steadily at the rate of 25 miles per hour (Terran). Gethenians could make their vehicles go faster, but they do not. If asked why not, they answer "Why?" Like asking Terrans why all our vehicles must go so fast; we answer "Why not?" No disputing tastes. Terrans tend to feel they've got to get ahead, make progress. The people of Winter, who always live in the Year One, feel that progress is less important than presence."

[kaybe]

Being faster in transporting people and things makes you better at wars and more prosperous in peacetimes (you can actually get fruit to the market before they spoil!). I don't think it's a simple matter of taste.

[jordonwii]

Well, one other phenomenon about Gethan is that they've never had a war, so it might be easier to get away with there. :)

[com2kid]

Average speed driving through SF is 18MPH, average speed in Boston is 20MPH. [Source: http://infinitemonkeycorps.net/projects/cityspeed/]

25MPH would be an improvement for a busy metro.

[wool_gather]

As with so many other things, average isn't really a good measure here. And unfortunately I don't think mode or median are really relevant either. It's the instantaneous speed that causes problems. Zooming up the block in a minute at 40 mph and then sitting at a red light for 3, your average was 10, but if you'd hit something, the damage you'd have done would be a lot worse.