one solution is better high speed commuter rail (or it's mere existence in the US) or other mass transit. mass transit is generally inherently more efficient. and stagnant rush hour is one of the single biggest pollution sources in a city. some amount of pollution is inescapable, but if rush can be reduced or nearly eliminated it can at least become limited to vehicles that are actually moving. commuter rail also has the advantage if increasing the feasibilty of accessing a city (for work or play) from larger distances, just like interstates and freeways initially did (before rush hour was invented). this allows access to cheaper land/real estate and lower costs of living. it helps outlying towns by providing more economic flow from the metro area. mass transit is great for everyone involved.
but it is ESPECIALLY good for the low income and poor folks stuck in the city.
problem is some (many) cities fight mass transit because it has the effect of allowing the "undesireables" to leave the inner city to locate work and housing in more affordable outlying areas. Specifically thinking of Atlanta, from experience, which has only 7 major transportation routes out of the metro during rush hour, the North and South bound legs of I75 and I85, and the E/W legs of I20, and GA400, along with a ring route I285. It DESPERATELY needs a metro line. But because Atlanta itself is only a portion of the area inside I285, and you have 8 different counties meeting there, there is no central authority to push it through.
this allows the outlying communities and counties to effectively kill any attempts at single real metro line, or other metro transportation system. Theres not even a single bus line. There's MARTA which operates only inside actual Atlanta (with a spur paralleling about 10 miles of GA400) and then each county and suburb has its only bus line. the result is you can't just board a single bus (or single company's bus) and ride it all the way into the city, you have change companies several times. This is incredibly inefficient, and its why no one relies on it who doesnt have to, and no one uses it to get from even slightly outside the perimeter (say, Smyrna) into downtown. The only people who use it are the less well off and poorer blacks in the city itself, and cheifly only to get around their surrounding area of maybe a dozen blocks. but it stays this way because the edges of the metro area DONT WANT those people (ie, black folks, especially poor ones) to be able to easily leave and settle outside the city, live outside the city while working inside it (or live in the city and access jobs on the edge of the metro complex...either way) , even though that kind of mobility would dramatically improve their lives and economic oppportunity. Those that can afford cars do move farther out, and join the rushhour, though again, rush hour imposes its own economic hurdles, in addition to the hurdle of getting a car (many of the folks stuck on the city dont have cars), but given the opportunity and infrastructure to make decisions that improve their family's situations, they do. And that scares many of the folks surrounding Atlanta.
Short version: The immobility of poor inner city populations leaves them stagnant and largely unable to change or improve their lives. A decent, efficient metro system changes that, opening up more opportunities, more mobility, more ability to choose and control ones circumstances, just by giving them access to more places to live and work. And the outlying communites fight such a concept tooth and nail. And its like that in many cities, not just Atlanta, and not just in the South.
It's one of the single biggest hurdles to improving our infrastructure and getting real, reliable mass transit, like high speed commuter rail, built.