Local Air Quality Management Districts in CA have been very active (and successful) in pursuing reductions in emissions from stationary sources (basically industry and small businesses), but responsibility for reducing mobile source emissions is outside their jurisdiction, falling to CARB (California Air Resource Board). We are now at a point where the majority of emissions come from mobile sources, so there needs to be more activity in this arena. Reducing traffic and emissions can work hand in hand if one uses a taxations scheme like London where alternative fuel vehicles are exempt. The money collected can then be used to provide incentives to EVs and other alternative fuel vehicles like natural gas vehicles (CNG, LNG).
If sucessful, this type of program could lead to a reduction in demand for diesel and gasoline in major metropolitan areas, reducing the price increase we'll see for these fuels when (if?) the economy picks up. In my opinion, EV adoption won't be high enough for the next 5-10 years to offset a major price increase in gasoline and diesel. Throw in CNG which already has a robust infrastructure in CA and other areas across th US and the equation changes. There are those that see natural gas use as just another hydrocarbon. The reality is it is mostly domestic (read NO money going to Saudis and from there to terrorists) and has much lower emissions (SOx, NOx and GHGs) than gasoline or diesel. It's not as good as EV, but it would work great as a bridge fuel as EVs develop. By the way, my wife and I currently drive 2 Civic GX's (CNG) so I'm definitely partial to CNG use over Gasoline and Diesel.
Having said all that, I wish Nissan would hurry up and give me a delivery date for my LEAF.