This may not offer a net savings in pollution, especially if the power was generated via a coal-fired power plant, but it gets the pollution out of the city and concentrates it so it is easier to deal with. Second, they are independent of the method used to generate the power. But, electric vehicles won't help us deal with congestion, and current battery technology is limiting. Also, battery transportation is a far greater mass penalty than excess-fuel transportation in a conventional car. It is currently not possible to support the claim that electric vehicles will reduce pollution.
Subways work well in urban areas of large cities.
But, they are extremely difficult to add to a modern city that does not already have them due to the network of pipes and cables that underlie any urban area. We need to keep our national population constant - but that is a topic for a different article. We need to start thinking of our transportation consumption not as a right, but as a necessary evil that should be minimized as much as possible. It should affect where we choose to live, where we choose to work, and how we choose our recreation. We need to be super-rational.