The ultimate solution to transportation pollution is using methods of transportation that don't pollute. For roughly a century, most transportation has been based on internal combustion engines (ICEs), which burn fossil fuels to produce energy and motion. And the residue from those burned fuels is where most transportation pollution comes from. One alternative method of transportation currently in the works is the fuel cell vehicle, which uses hydrogen as a source of electricity that in turn runs a motor. The only exhaust from a fuel cell vehicle is steam, which isn't a pollutant. Unfortunately, fuel cell vehicles are in an early stage of development and are only available currently as prototypes. It'll be a while before you find one at your neighborhood automobile dealership. But when they become available, they'll provide an excellent solution to the transportation pollution problem.
Get a fuel cell vehicle (when they're available)