DETROIT — Ford Motor Co. said Tuesday it sold a record 11,600 natural gas vehicles last year, more than four times the number it sold two years ago.

It’s the latest sign that natural gas is making inroads as a transportation fuel, particularly for truck fleets, buses and taxis. The consumer market is tougher to crack, but sales are gaining there as well.

Natural gas is cheap and plentiful in the U.S. after a spike in production that began in the middle of last decade. At the same time, the price of gasoline and diesel fuel has jumped more than 30 percent.

That makes natural gas – which also emits fewer greenhouse gases – an increasingly attractive option for truck companies and municipalities.

But while natural gas may be a good choice for snowplows and trash trucks, which go relatively short distances and can refuel at city-owned pumps, it’s a tougher call for ordinary consumers. Natural gas cars cost more and there are few public places to refuel them. Those issues need to be addressed if the vehicles are to significantly boost their share of the auto market, which is currently less than 1 percent.

General Motors Co. and Chrysler Group recently added natural gas pickup trucks to their lineups. Honda Motor Co. is seeing more interest in its natural gas Civic – with record U.S. sales of nearly 2,000 last year — and industry experts expect more offerings for regular buyers in the next year or two.

Compressed natural gas – or CNG – costs $1.79 to $3.49 per gallon in the U.S. depending on the location, according to Clean Energy, which operates natural gas fueling stations, and AAA.

It’s even cheaper for corporate or government buyers, who may pay as little as 80 cents per gallon for their natural gas, according to CNG Now, an industry lobbying group.

Honda and Chrysler are the only companies that make CNG-ready vehicles in their own factories. Ford and GM make vans and trucks that are prepped to run on CNG, or on a combination of gasoline and CNG, but rely on outside companies to add about $10,000 worth of equipment, including the natural gas tank.

GE, which is developing a home fueling station, estimates that 250,000 natural gas vehicles are now in use in the U.S.