Over the road trucking (OTR) represents one of the greatest opportunities for natural gas to be used as a transportation fuel. These heavy-duty high-mileage trucks consume a lot of fuel and benefit from the lower cost of natural gas. Using natural gas in OTR applications reduces costs for shippers, carriers, as well as the end-user or consumer. The introduction of the Cummins Westport 12L ISX-G 400 HP natural gas engine in 2013 opened the door for many companies to begin transitioning to natural gas. The Cummins Westport 8.9L ISL-G engine also sees use in some OTR applications, but 12L ISX-G engine provides the horsepower required by most OTR applications. These engines are available on truck models from most heavy-duty truck manufacturers, including Freightliner, Kenworth, Peterbilt, Volvo, Mack, and International. Fleets are now deploying natural gas trucks that operate on either compressed natural gas (CNG) or liquefied natural gas (LNG). Both forms of natural gas have advantages in OTR applications, and the number of “truck-friendly” public CNG and LNG stations is expanding rapidly. Many of these are strategically located near major highways, often at pre-existing truck stops to support cross-country travel.

Collaboration between Shippers and Carriers
One of the challenges facing the adoption of natural gas in over the road trucking operations is that many of the heavy-duty trucks operating in this sector are owned by carriers, or contractors, that operate routes on behalf of shippers. This adds an added layer of partnership and collaboration that is not present in other market segments and must be negotiated. Shippers are attracted to the environmental and economic benefits of natural gas that help achieve corporate sustainability goals as well as help lower operating costs. Many national shippers are maintaining contracts and awarding new contracts to carriers based on their transition, or willingness to transition, to natural gas.

Some carriers that do not operate on fixed routes may be concerned about being unable to accept a job due to lack of fueling infrastructure. One solution is for shippers to work together to ensure round trips are supported with natural gas infrastructure along routes used by their carriers. Many positive shipper-carrier relationships have developed to deploy extensive NGV fleets. Dillon Transport, a truck carrier based in Burr Ridge, Illinois, is a 2013 NGV Achievement Award winner for its natural gas fleet program. Dillon currently operates more than 200 natural gas units that is a mix of both LNG and CNG tractors. The company’s policy of utilizing public fueling infrastructure has resulted in the creation of several new public natural gas stations in the areas in which they operate.

Efficiency and Emissions
The U.S. EPA and NHTSA finalized fuel economy (FE) and greenhouse gas (GHG) requirements for medium and heavy-duty vehicles. The regulations start to take effect in 2014 and are fully phase-in by 2018. The fuel efficiency regulations actually lag the GHG rules by two years, not taking effect until 2016. Summarizing the rules is not easy because the rules are extensive and establish different requirements for different types of vehicles. The phase-in periods and levels of stringency also vary depending on whether an engine is spark-ignited or compression ignited. When implemented, the standards for combination tractors would achieve a 9 to 23 percent reduction in emissions and fuel consumption compared to 2010 baseline levels. The GHG rules regulate CO2 emissions by imposing an overall fleet-wide average for manufacturers, but impose a per vehicle/engine cap on methane and nitrous oxide (NOx) emissions. Manufacturers that have trouble meeting the caps imposed on these other pollutants may use CO2 credits to offset them. The methane cap finalized for heavy-duty engines is 0.10 grams per bhp-hr.

Natural gas engines typically suffer a loss of fuel economy that can be as much as 10 percent when compared to equivalent diesel engines. This is due to the nature of spark-ignited engines versus diesl compression engines. Engine manufacturers are working to make improvements to the fuel efficiency of natural gas motors, and truck manufacturers are working with operators to make improvements to the design and operation of vehicles to make them more efficient. Some strategies include optimizing transmissions, integrating natural gas tanks in to the body of the vehicle to improve aerodynamics, and using fuel efficient, fully inflated tires.

Available Vehicles
There are a number of OEM and aftermarket options for the over-the-road market. For more information and a complete list of EPA and CARB certified vehicles and engines, visit the Vehicle Availability page.

The U.S. Department of Energy’s (DOE) Alternative Fuels Data Center (AFDC) provides an online tool that lists available alternative fuel vehicles from leading OEMs.  To view a list of heavy duty natural gas tractors currently available, visit the Alternative Fuel and Advanced Vehicle Search.