This could occur in a number of ways. As natural gas supplies have increased and prices have dropped, automakers and truck manufacturers have begun taking steps to introduce new vehicle lines fueled by natural gas, principally compressed natural gas (CNG) and liquefied natural gas (LNG). On an energy-equivalent basis, oil has been more expensive than natural gas in recent years. Only 2.9% of U.S, natural gas production is currently used in transportation, mainly to move gas through the pipelines, and expanded use of natural gas vehicles would likely lead to increased demand for natural gas. Among the key factors determining the attractiveness of natural gas as a transportation fuel is its price relative to diesel fuel. Some of them require pressurized systems to burn the fuel in a gaseous state, and others convert natural gas to a liquid. The vehicles return each day to a central garage or maintenance yard, where refueling infrastructure may be installed. Long-haul trucks are a target market for use of LNG because of the fuel's price advantage and environmental benefits over diesel fuel. In addition, LNG is most effective when the vehicle it fuels is used regularly, such as long-haul trucks. It is known as autogas or liquefied petroleum gas (LPG) when used as a motor vehicle fuel. Hydrogen, produced mainly from natural gas, can be used to power fuel cell vehicles. Natural-Gas-Based Electricity

Spurring the production and use of electric vehicles is another way to use natural gas in vehicles. Prospects for Growth

Future consumer and commercial interest in natural gas vehicles hinges on the relative price of petroleum to natural gas, refueling infrastructure, environmental concerns, federal and state incentives, and the price of natural gas vehicles relative to traditional gasoline vehicles. Cars and CNG

Natural gas fueling is less expensive than gasoline. Similarly, if there are fewer fugitive emissions, total lifecycle emissions would be lower. Congressional Involvement

As the availability of domestic natural gas supplies has increased, so too has congressional interest in finding ways to use more natural gas in the transportation sector. Legislation to promote natural gas as a vehicle fuel has been introduced in the 113 th Congress (and in previous years), including proposals that would change the taxation of alternative fuels and vehicles, modify the regulation of natural gas vehicles under federal CAFE standards, increase the weight limit for natural gas trucks on interstate highways, provide loans and grants for deployment of alternative fuel vehicles and recharging stations, and raise federal agency use of alternative fuel vehicles. A broad energy efficiency bill ( S. 761 ) reported out of the Senate Energy and Natural Resources Committee on June 3, 2013, includes a provision (Section 403) amending the National Energy Conservation Policy Act to authorize the use of energy savings performance contracts and utility energy service contracts for projects that support the use of natural gas and electric vehicles or the related fueling or charging infrastructure. S. 1486 , the Postal Reform Act of 2014, among other provisions, would require the postmaster general to submit a report to Congress on the feasibility of a pilot program to use natural gas and propane in U.S. 3940 and S. 2721 , Natural Gas Long Haul Truck Competitiveness Act of 2014 , would require DOT to issue regulations to allow natural gas vehicles to exceed federal weight limitations to operate on U.S. interstate highways by an amount equal to the weight of the vehicle's natural gas tank and fueling system, less the weight of comparable diesel tanks and fueling systems.
The increase in domestic supplies of natural gas has raised new interest in expanding its use in the transportation sector. This report considers issues related to wider use of natural gas as a fuel in passenger cars and commercial vehicles.
The attractiveness of natural gas as a vehicle fuel is premised in large part on its low price (on an energy-equivalent basis) compared to gasoline and diesel fuel. When prices for gasoline and diesel are relatively low or natural gas prices are relatively high, natural-gas-based fuels lose much of their price advantage. While natural gas has other benefits—such as producing lower emissions than gasoline and diesel and protecting users of transportation fuels from the volatility of the international oil market—it is largely the cost advantage, if any, that will determine the future attractiveness of natural gas vehicles.
There are a number of technology pathways that could lead to greater use of natural gas in transportation. Some require pressurized systems to use natural gas in a gaseous state, and others convert natural gas to a liquid. Two of the most widely discussed options use compressed natural gas (CNG) and liquefied natural gas (LNG). Other technological approaches use liquefied petroleum gas (LPG), propane, and hydrogen. In addition, natural gas can be used to generate electricity to power electric vehicles.
Increasing the use of natural gas to fuel vehicles would require creation of an extensive nationwide refueling infrastructure. Although a small number of CNG vehicles have been on U.S. roads for more than 20 years, CNG use has been limited to vehicles that return to a central garage for refueling each day, such as refuse trucks, short-haul trucks, and city buses. LNG, on the other hand, requires large insulated tanks to keep the liquefied gas at a very low temperature and is therefore seen as more suitable for long-haul trucks. In both cases, the limited availability of refueling stations has limited the distances and routes these vehicles may travel.
Congress has taken a strong interest in spurring production and use of natural gas vehicles. Legislation has been introduced on a wide range of proposals that would equalize the tax treatment of LNG and diesel fuels, provide tax credits for natural gas vehicles and refueling equipment, require the production of vehicles that could run on several different fuels (such as gasoline and CNG), increase federal research and development on natural gas vehicle tank and fuel line technologies, and revise vehicle emission regulations to encourage manufacturers to produce more CNG passenger cars.
Legislation pending in the 113th Congress includes proposals that would extend expired tax credits for refueling property and fuel cell vehicles (S. 2260), authorize the use of energy savings performance contracts to support the use of natural gas and electric vehicles (S. 761), and require the U.S. Postal Service to study the feasibility of using natural gas and propane in long-haul trucks (S. 1486).