Traffic Theory of Urban/Metropolitan Areas

This is my new theory about the relationship between traffic and urban/metro populations. The greater the difference between the urban and the metro population, the greater the traffic that city has in porportion to its size. Factors such as density, use of mass transit...etc affect this theory. This applies to many U.S. cities. Look at Los Angeles, America's worst traffic place. L.A. urban population is 12 million while its metro is 17.5 million. That is a significant difference resulting in heavy traffic and since it's a very large city, it has HORRIBLE traffic. New York's urban population is 18 million while its metro is 22 million. Not as significant difference as Los Angeles therefore it has less traffic problems. But since New York is HUGE, it's common for it to have heavy traffic. Remember the traffic in porportion to the city's size and the density as well. Chicago's urban population is 8.3 million and its metro is around 9.6 million. Not a very large difference, but Chicago is a very large city therefore traffic is common, and the size of Chicago's highways are a factor making Chicago's traffic worse than it should be. I hear some people in this forum complain about Chicago's highways are too narrow and should have more lanes. Philadelphia's urban population is 5.2 million and its metro is 6 million. Not a very big difference therefore less traffic problems and the use of mass transit benefits as well.>