I recently found out that all of the busses in Boise run on Natural Gas and not Diesel. I'm wondering, if this is such a cost effective and clean fuel for busses, why not cars?

There has to be some drawback, do cars that run on Natural Gas have performance problems like speed? I can see how this would make it feasible for a city bus and not a car.

RoverRoad

It may be before long. One of the main stumbling blocks with any new energy source for cars is a distribution network. To have natural gas powered buses you only need a single station where the buses are stored. For a car, you need one anywhere that the driver might go (other cities)

Pros:
slightly cheaper than gasoline (currently... see cons)
cleaner than gasoline

Cons:
prices fluctuate. Increased demand (which is increasing anyway due to methane's increasing use in heating and electricity generation) could make the prices higher than gasoline.
drilling disrupts the environment.
vehicles must have high pressure, heavy, larger tanks
high exploration costs would have to be paid to find enough if its use really took off.
not as much of an improvement over gas (or especially the new hybrids) as it is over the diesel buses run on.

Natural gas might be the easiest transition to make, but it would still not be simple. The fact is, until the demand is there or regulations are made, it's just not profitable to automakers and fuel distributors. Even those who are willing to spend a large amount of money for a more environmentally friendly car wouldn't necessarily go for natural gas. It's more environmentally friendly than gasoline, but still far from perfect.

Interest is increasing, so it may be a reality in the not-too-distant future.

Such buses are very common in Europe. There are signs that cars running on it are becoming more common; every underground car park I see in Cannes and Nice in the South of France now has a notice at the entrance about them.It says that vehicles so propelled will not be admitted unless they have approved safety taps fitted; we may suppose that some conversions to such gas are less than professional !