Like twigs going down a drain or people through a doorway: if vehicles travel through areas of high traffic congestion one at a time, at the same speed, they will all maintain a higher average speed.
Don't worry. Since neither urban sprawl nor population density is going to reduce in the future, your drive-by-wire throttle will automatically reduce your speed depending on the vehicle's GPS coordinates.
Tickets will be instantly deducted from your account via the cell phone.
These systems, of course, will be required on all registered vehicles, but "important" people and risky tweakers will still be able slalom around the herd, at least for a while.