DETROIT – More natural gas-powered vehicles will hit the market soon, as rising gasoline prices, booming natural gas production and proposed tax credits make them a more attractive option. But they’re a long way from being a common sight in U.S. driveways.

Starting in July, Chrysler will sell a Ram 2500 Heavy Duty pickup that runs on compressed natural gas (CNG). The truck has both gasoline and natural gas storage tanks, and the engine shifts automatically between the two, without the driver needing to push a switch. The truck can run for 255 miles on natural gas, and the range is extended to 367 miles using gasoline.

Chrysler will have competition. Late this year, General Motors Co. will sell natural-gas versions of two pickups: the Chevrolet Silverado and GMC Sierra 2500 HD. The GM trucks will run on gasoline and natural gas for 650 miles. Ford Motor Co. has offered natural-gas ready pickups and vans since 2009.

Natural gas is appealing for a lot of reasons. It comes from domestic sources. It produces 30 percent fewer greenhouse gas emissions than traditional gasoline or diesel. And it costs less than gasoline because of abundant production and supplies in the U.S. Natural gas prices have dropped more than 23 percent this year. Regular gasoline prices have climbed 23 percent over the same period.

At the pump, drivers paid an average of $3.37 a gallon for gasoline in January. That compared with $2.13 a gallon for compressed natural gas, according to the latest government data.

But U.S. buyers have been slow to adopt natural-gas vehicles, which make up less than one-tenth of 1 percent of the vehicles on American roads. Even the newest trucks aren’t intended for average buyers. They’re work trucks, capable of plowing snow and towing three tons or more. Chrysler will only sell its natural-gas Ram to fleet customers. GM anticipates that 90 percent of its sales will be to fleets.

Here are some reasons that U.S. buyers have been slow to adopt natural-gas vehicles:

n Lack of fueling stations. There are around 1,000 natural-gas fueling stations in the U.S., but only half of them are open to the public. Most are operated by local governments or private companies to refuel buses and other fleet vehicles. California-based Clean Energy Fuels Corp. aims to install natural-gas pumps at 150 truck stops nationwide over the next few years. But that pales in comparison to the availability of gasoline.

n Few choices. There is only one factory-built natural-gas car sold in the U.S. It’s the natural-gas version of the Honda Civic. About 13,000 have been sold since the car went on sale in 1998, mostly to fleets.

n Cost. Additional fuel tanks and parts and small-scale production make natural gas vehicles more expensive. The CNG Ram, for example, starts at $47,500, almost $20,000 more than a base Ram 2500. The natural-gas Civic starts at $26,155, or $10,000 more than a base four-door Civic.

GM won’t announce the price of its natural-gas trucks until next month, but expect a premium.