Here is a way of taking heavy traffic (and air pullution) from some cities, not all but most.
No more cars, nor public transportation nor any kind of wheeled nor fueled vehicles on streets... except emergency ones... sounds strange... but think about this idea... instead of having all those cabs n buses
n cars n etc... streets would be only for pedestrians... ahhh.. hear the sound of silence??
you may ask: How do you go somewhere without transportation?
Well... streets would be divided in two parts, one side for emergency transportation, and in the other side of street there would be for large transportation belts (?, excuse my english is not my native language).. with seats where you can sit (well...)... this belts could be covered with some kind of transparent protection for rainy days... and would travel at 8 mph.. so you can "get up" or "down" from this transportation... anywhere you like.... (in front of your house.. or in front of your office).. and in main streets you would have.. lets say.. 7 rows of belts so the outermost belts would travel at 8 mph.. next inner belt at 16 mph next at 24 mph.. and the belt in the center at 32 mph... maybe more belts in wider streets.. or maybe a better distribution, where you can get in or out from only one side.
So if you need to go faster you ride an inner belt.. this 8 mph step from belt to belt would let people to get the 32 mph belt in steps.. so you always need to "jump" to a belt moving at 8 mph (it won't be really a jump...), remeber relativity. So you would be able to travel to places where heavy traffic used to be.. at a speed of almost 32 mph constant... without redlights... without traffic.. without any kind of stops... I think this is a more fast way of getting some places in some kind of cities where traffic solutions are almost impossible.
This would also let you calculate traveling time more accurately... so you can sleep some minutes more.. you would be able to say .."well I take the 8 mph belt from home to xx main street..(lets say 1/4 mile) n there I get the 32 mph belt to my office (lets say 3 miles)... that would be no more than 8 minutes counting "getting in" or "down" from belts..."
Maybe one problem would be pedestrian crossing streets.. well maybe this belts could be "half-underground" with their transparent celling.. and in intersections... high speed sets of belts would pass straight over "low order" crossing belts, these would go little deeper into the ground so "high order belts" can pass straight, without "up hills" nor "down hills"...it would not be comfortable because of speed.. and for "low order belts" height is not so important because it needs to be enough so people could fit sitting in the "mounted-on-belt-chairs"
And the best of all things.. these kind of transportation only needs electricity.. nor pollution at all... no more noise... and even I think this kind of transportation must be free for everyone.
Well some technical things would need to be solved.. like extension of belts... waste of energy in empty belts... etc... but that is not my job... hehehe.