Constant-speed fuel consumption testing of heavy-duty vehicles in India

As policymakers in India deliberate on how best to design a regulation to improve the efficiency of new heavy-duty vehicles (HDVs), one of the most critical issues is what test methods and duty cycles will be utilized to evaluate fuel efficiency performance. Ideally, a regulatory test procedure should test a vehicle, engine, or piece of equipment in a manner that closely matches the expected real-world conditions. That way, regulators, manufacturers, end-users, and society at large can have con dence that the efficiency measured over the regulatory test accurately reflects the efficiency of the vehicle in-use. It is the ICCT’s position that an engine standard, coupled with a regulation promoting more fuel-efficient tires, will maximize fuel and emissions benefits most rapidly and put India on the best path forward. Another testing approach that is garnering attention in the regulatory discussions in India is constant-speed fuel consumption (CSFC) testing. As the name implies, in this test procedure the vehicle is driven on a test track at constant speed.

The overall goal of regulation should be to incentivize manufacturers to design their engines and vehicles to operate efficiently across the range of operating conditions that are typically encountered on the road (i.e., accelerating, decelerating, cruising, idling). Our analysis shows that CSFC testing only exercises the engine at a very tightly bound point on its operating map and does not capture any of the diversity of in-use driving. Engine dynamometer testing offers a more cost-effective and robust way to simulate a broad range of both steady-state and transient conditions. Engine-based standards coupled with a tire efficiency regulation is ICCT’s recommended approach for the first phase of India HDV efficiency standards. Nevertheless, even a CSFC-based efficiency standard, if it were established soon, would be preferable to a long delay in order to design a regulatory program centered around sophisticated vehicle simulation software, which will take many years to develop, validate, and implement. Despite its downsides, efficiency improvements over the CSFC cycles will likely translate to real-world improvements.