Medium- and heavy-duty vehicles (MHDVs) represent less than 5 percent of the total vehicle market today, and the vast majority of these use conventional internal combustion engines (ICE) powered by either gasoline or diesel, according to Navigant Research.

That is changing as less expensive alternatives to petroleum-based fuels, such as natural gas, liquefied petroleum gas (also known as propane autogas), and electricity make inroads in the market. According to a new report from Navigant Research, worldwide sales of alternative fuel vehicles will reach 14 percent of total sales of medium and heavy duty vehicles by 2035.

“Attractive business cases for medium- and heavy-duty alternative fuel vehicles are emerging across varying segments of the market,” says Scott Shepard, research analyst with Navigant Research. “Natural gas has a significant advantage over most alternative fuels, in that low fuel costs and advances in infrastructure for both liquefied natural gas and fast-fill compressed natural gas make the fuel competitive in all market segments, including heavy-duty long-haul trucking.”

The total number of MHDVs in use worldwide will nearly double between 2014 and 2035, according to the report. According to Navigant, unlike light-duty vehicles, most of today’s MHDVs are fueled by diesel fuel. While diesel will remain the primary fuel choice of MHDVs throughout the forecast period, the percentage of MHDVs powered by diesel is expected to fall from more than 79 percent in 2014 to 76 percent in 2035.

The report, “Transportation Forecast: Medium and Heavy Duty Vehicles”, analyzes the global MHDV market in seven segments: conventional ICE vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, natural gas vehicles, propane autogas vehicles, and fuel cell vehicles.

Forecasts for two segments fueled primarily by petroleum derivatives (ICE and hybrid electric vehicles) are broken out by region and by fuel: gasoline or diesel. Global market forecasts for sales and conversions and the number of vehicles in use, segmented by country, drivetrain, and primary fuel, extend through 2035, according to Navigant.