[throwaway0a5e]

Obviously you can't have traffic going 60mph in Manhatten but to a point everyone benefits.

Uneven traffic flow results in a lot of lane changing and passing and when drivers are preparing to do those moves they're spending a lot of effort figuring out where the cars are and that creates a prime opportunity for anything motorcycle and smaller to be missed.

So yeah, a uniform 30ish MPH traffic flow on your city street is probably better than a more bimodal one even if the average speed is slightly higher.