Mack Trucks Inc. is manufacturing a four-axle, heavy-duty dump truck for the U.S. Army that is offered with either a standard cab with a special, poison gas-resistant coating or a heavily armored cab.

Even with the best basic specs, additional fuel savings will come from substituting a single drive axle for the standard tandem axle drive system.

Adjusting overhead valves on heavy-duty ­diesels is a routine maintenance item subject to benign neglect in many of today’s fleets. But factory engineers are split on the importance of frequently setting overheads.

As state and federal clean-air regulators move forward with plans to further reduce nitrogen oxide and particulate matter emissions from commercial trucks, diesel engine makers are exploring new technologies to meet those targets in the coming years.

Achates Power of San Diego has developed a two-stroke truck diesel that has two crankshafts linked to two opposed pistons facing each other in a common cylinder.

Hydrogen will likely end up as the dominant fuel for longhaul trucks one or more decades from now, according to experts at familiar component suppliers and truck manufacturers. Nikola Motor Co. agrees, as one of the first entrants into this arena, with a whole new vehicle architecture.

Researchers have developed a promising yet surprisingly simple modification to diesel engines that could hold the key to reducing the complexity, maintenance, and size and weight of emission aftertreatment systems.

The introduction of electric-­powered trucks represents a new frontier for the transportation industry, but this new breed of commercial vehicle will not be completely unfamiliar to fleets and maintenance shops.