Jerry Hirsch:

Natural gas is the neglected stepchild of the alternative fuel vehicles industry.
 Used in some commercial truck fleets, municipal bus services and the occasional taxicab, the plentiful low-emissions fuel has never caught on in passenger cars — even though it sells for about half the equivalent of a gallon of gasoline in California.
 Two automakers are making another run at selling compressed natural gas, or CNG, cars in the U.S., eyeing a market in commuters and efficiency-minded drivers.