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An in-depth comparison of CU’s passenger vehicle average MPG estimates with those published by EPA and NHTA


Michael S. Saccucci, Ph.D.
Director, Statistics & Quality Mangement
R. David Pittle, Ph.D.
Sr. Vice-President, Technical Policy (retired)
David Champion, B.S.M.E.
Sr. Director, Auto Test
K. Newsom-Stewart, Ph.D.
Senior Statistician
Sally Greenberg, J.D.
Senior Product Safety Counsel
Anita Lam, M.S.
Automotive Data Program Manager
Consumers Union
101 Truman Avenue
Yonkers, NY 10703
August 11, 2005

Consumers Union (CU) has had a longstanding public concern about the national need to require better vehicle fuel economy across the fleet of passenger vehicles. America’s dependence on foreign oil is a national security concern. The fact that two-thirds of the oil consumed in the United States today is used for passenger vehicles tells us that the nation needs to accurately assess and improve fuel efficiency to the maximum extent possible, consistent with what is technologically and economically feasible. We are also concerned with the effects of ever-increasing emissions on air quality, on the environment, and the increased threat of global warming. All of these problems make accuracy in fuel economy ratings more immediate than ever.
Currently, the Environmental Protection Agency (EPA) uses a dynamometer-based testing system to estimate city and highway miles per gallon (MPG), and uses these to compute an overall MPG estimate. The city and highway estimates are based on an urban/suburban/highway driving cycle that was developed in the 1970s and replicated the type of driving conditions that were typical then. Today, the driving conditions are very different; there is more freeway driving, both cruising and stop-and-go in rush hour traffic. Highways are generally posted for 55 mph and, although many sections of the U.S. interstate system are restricted by a 55-mph speed limit, there are numerous sections posted for 65 mph and higher. The EPA recognizes that its preliminary fuel economy estimates are overstated, and downweights them for posting on new vehicles at the point of sale. Despite this, Congress has mandated that the National Highway Traffic Safety Administration (NHTSA) use the preliminary, unadjusted estimates to evaluate compliance with Corporate Average Fuel Economy (CAFE) standards. (See the NHTSA website at www.nhtsa.dot.gov for a detailed description of the CAFE system.) This approach forces CAFE assessments yet further away from real-world experience.
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