I live on a one-way residential street which is 20mph and has been "traffic-calmed" by the addition of road-humps.
Suffice to say that the number of drivers sticking to 20mph or less is dissappointing. The road isn't very long, and is quite narrow, but still some clever clogs manage to really put their foot down.
Except today, I saw a driver gingerly approaching each speed hump at walking pace and carefully negotiating the road. Why? Because they were driving a Ferrari that was so low to the ground anything over 10mph would have taken the front of the car off as it went over the road humps. There was something very satisfying by the normal trail of traffic being slowed by one of the fastest cars in the world.
So there we have it. If we want all drivers to negotiate our traffic calmed roads slowly and carefully we should give them all Ferraris....