I have stated several times here that I believe urban freeways have their place in most cities, particularly in cities with lots of industrial and military activity. These are the purposes for which a federal highway system was created.
Unfortunately, these highways were not created for what they are most commonly used to accomplish: commuting. Most traffic congestion is caused by commuting. It occurs in the morning and evening rush hours. It costs trillions in wasted fuel, wasted time, and wasted environment.
What if commuting on highways was illegal?
This is a highly unlikely and rather radical approach to solve widescale congestion problems, and I have no reason to think it would take anywhere in the US right now. But what if urban freeways (like 295 and 395, for instance) were reserved only for transit, industrial (trucks), military, and emergency vehicles? Naturally this would have to come with an unrealistically large scale repurposing of our suburbs, which is why it is obviously not feasible. This hypothetical line of thought could argue a couple of advantages in the case of Washington, DC.
This would mean commuters would need to find alternative means of getting to DC. This would undoubtedly result in thousands of cars being taken off the road. the lack of cars commuting into or through the city would result in less space needed for commuter parking, which could allow more parks, residences, and businesses to be constructed throughout the city. It would likely result in a massive drop in car owners. This would increase the disposable income of area residents who no longer have need to own a car. (I have stated before that for me, this would be about 20% of my take home income). That would result in a higher tax base for the city, making it easier to invest in an expanded mass transit system, perpetuating a cycle that would reverse the negative effects of sprawl.
Industrial and military vehicles would be less likely to use the surface streets. In fact, they could even be outlawed from using surface streets, apart from approaches to the highways. though it might inconvenience some industrial traffic, I imagine that having an uncongested freeway would be an overall benefit for them. I am vehemently opposed to having military traffic running down city streets. To me this is something that they do in Tehran and Pyongyang, not Washington, DC.
Naturally, the drop in gas usage, exhaust, and vehicle miles traveled will be good for our environment. One could even go so far as to suggest that there would be an overall increase in walking, which could lead to better health. But more directly, the decrease in CO2 emissions will have an obvious and immediate impact on air quality.
Freeways are valuable tools of industry in America. They literally shaped the landscape and united the country in a way the world had never seen before. But they have been rendered near useless in much of the country becasue we allow them to be used for purposes which they were not originally intended. Perhaps rethinking the modality of freeways on some level could benefit a the local, municipal, regional, and national landscapes.