How far you can get from downtown in rush hour traffic?
The city where you can travel the shortest distance in rush hour is Miami. This is misleading, however, because the city is jammed against the coastline, so all the traffic leaving the city must go west.
By another definition, the most congested is Boston, because there is the greatest difference between how far you can travel in rush hour versus late at night.
The least congested is Las Vegas, where you can travel more than 50 miles at any time of day. This is the anti-Miami, in that it is in a wide-open desert, so the traffic moves away from the central city in many different directions, all on excellent highways.