As U.S. regulatory agencies work on the second phase of heavy-duty vehicle greenhouse gas (GHG) and efficiency standards, one key issue is understanding how available and emerging technologies might increase tractor-trailer efficiency by 2020 and beyond.
This analysis incorporates a new 2010-emissions-compliant engine map and its detailed energy audit in modeling tractor-trailer technology using the U.S. Department of Energy’s Autonomie vehicle simulation platform. The resulting model, based on data from the literature and industry developments, evaluates emerging engine, transmission, and road load reduction technologies individually and in several technology packages.
- Technology potential in the mid term. Available tractor-trailer efficiency technologies can reduce fuel use per ton-mile by almost 40% from the baseline 2010 technology before 2025.
- Technology potential in the long term. Emerging load-reduction and powertrain technologies can achieve at least a 50% fuel-use reduction from baseline 2010 technology in the 2025–2030 time frame. For the regulation to be technology-forcing, it would need to ensure these levels of fuel-consumption reduction and build in sufficiently long lead times to promote all the promising advanced efficiency technologies.
- Diverse technology approaches. Technology packages with advanced load-reduction and engine energy recovery approaches can achieve similar efficiency results, but do so with varying relative contributions from aerodynamic, powertrain, and other improvements. The regulatory structure should ensure that all available cost-effective technologies, from engines to trailers, are strongly promoted.
- Engine efficiency potential. The analysis of technology packages indicates that one-third to one-half of the overall potential tractor-trailer efficiency benefits come from engine efficiency improvements (from baseline 2010 technology). Without sufficient engine-specific regulatory requirements, these engine-efficiency technologies appear unlikely to be commercialized in the 2030 timeframe.
- Regulatory procedure changes. Direct use of engine map data for regulatory accounting of engine efficiency in integrated full-vehicle simulation, inclusion of grade in test cycles that better reflect real-world driving, streamlined procedures that promote emerging integrated engine-powertrain options, and requirements for trailer efficiency can all help promote applicable and promising technologies according to their real-world benefits.