Global sales of medium- and heavy-duty vehicles should reach 7.1 million by 2035 from the 4.3 million that are expected to be sold in 2014, according to a new report from Navigant Research.

In a report that analyzes global market forecasts by country, drivetrain, and primary fuel, Navigant notes that the global market for these vehicles represents less than 5 percent of the total vehicle market today, yet they use a far greater portion of the total fuel and energy consumed in the road transportation sector.

Nearly 80 percent of the medium and heavy duty trucks and vans now run on diesel fuel, according to the report. In recent years, fuel costs and environmental concerns have pushed commercial and government fleet operators to consider investments in fuel efficiency technologies and alternative fuels. The most competitive alternative fuel, according to the report, is natural gas, which has a significant advantage over most other alternatives to gasoline and diesel.

“The vast majority of MHDVs on roads today use conventional internal combustion engines powered by either gasoline or diesel,” said Scott Shepard, research analyst with 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.”

For more information or to download the full report, click here.