Long combination vehicles (LCV) are multi-trailer combination vehicles weighing more than 80,000 lb gross vehicle weight rating (GVWR). Where 120,000 lb GVWR is permitted, turnpike doubles could haul additional freight with 15–39% less energy per ton-mile than a standard single. For loads that don’t reach maximum weight capacity but run out of trailer space because of bulky, non-dense products (“cubed-out” loads), a second trailer could double the amount of cargo delivered without exceeding GVWR. If the load “weighs out” first, the fuel saving per ton-mile falls to 15%.
Only 22 states allow trucks to weigh more than 80,000 lb. Harmonizing laws to permit higher weights and longer vehicles would allow U.S. fleets to deliver more freight per trip using less fuel per ton-mile delivered.
LCVs also imply a number of operational (wider turning lanes, logistical changes), physical (pavement load distributions), and infrastructure impacts (bridge weight limits, road geometry considerations). Notably, though, well-designed LCVs can reduce road wear and congestion while improving safety.
Ogburn, Michael, Laurie Ramroth, and Amory Lovins. 2008. Transformational Trucks: Determining the Energy Efficiency Limits of a Class-8 Tractor-Trailer. Snowmass, CO: Rocky Mountain Institute, July. link