SAE International The Impact of Lift Axles on Fuel Economy and GHG Emissions Reduction 2015-01-2874

Using lift axles enables fleet to increase the load capacity of a vehicle, eliminating the need for multiple trips, thus reducing operational costs. In a project to assess the potential of reducing fuel consumption and greenhouse gas (GHG) emissions by lifting axles on unloaded semi-trailers, lift axle regulations in various jurisdictions and the studies that led to these regulations were analyzed. The SAE Fuel Consumption Test Procedures Type II (J1321) was used for fuel consumption track test evaluations. The tests were conducted on unloaded two-axle van semi-trailers, four-axle van semitrailers, and B-trains, and resulted in fuel savings of 1.3% to 4.8%, depending on vehicle configuration and the number of axles lifted during the test. Temperature measurements and thermal images taken during the tests show that the difference in temperature of rolling tires of tandem axles with one axle lifted, compared to the temperature of rolling tires of tandem axles with both axles on ground was minimal. As such, lifting the axles of unloaded van semi-trailers shows an interesting potential in fuel savings and GHG emissions reduction because in many applications, semi-trailers travel unloaded 50% of the time. Special equipment is however necessary to lift axles and there are regulatory constraints regarding these devices. Several Canadian provinces allow the lifting of axles when a semi-trailer is empty, however, additional studies are necessary to evaluate the impact of lift axles on maintenance (tire wear) and safety (braking performance).