Absolutely Bob, and that is the cornerstone of the Pickens plan - use natgas for transportation. Its plentiful, cheap, clean, and requires very little refining in most cases. Here's the issues with it currently as I understand them:
1. Transport of gas to areas where it can be used. Gas can't be put on a rail car or truck and carted around the country (economically anyway). The only way is via pipeline, which means every single little gas well has to be interconnected to a main pipeline. VERY expensive to lay down millions of miles of pipe and you run into the problem with "not in my backyard" everywhere you try to lay down a pipeline route, so you have to buy up all the land the pipe runs through.
2. Conversion of cars, trucks & trains to run CNG and conversion of millions of service stations to store CNG under very high pressure and dispense CNG safely. You have to factor in that most service stations are not owned by Big Oil anymore, they sold those to thousands of individual biz owners. It says Shell on the sign but its not owned by Shell, they just sell Shell's gas. The costs are huge and there are safety issues with cars & trucks with pressurized explosive gas running around. Not insurmountable, but very expensive
It would take a massive gov't commitment to get this started and invest in the infrastructure. Even Big Oil can't afford this kind of investment.
Nuclear is the same deal - no one wants a plant in thier city and no one wants nuclear waste transported through thier city to a safe storage facility. Everyone screams at thier local leaders to stop it...and they do.