Report suggests that not following good eco-driving practices can lead to a reduction in on-road fuel economy of up to about 45% in total
8 September 2011
The types of vehicles consumers select has by far the most dominant impact on on-road fuel economy—the best vehicle currently available for sale in the US is nine times more fuel efficient than the worst vehicle. However, remaining factors over which a driver has control—route selection; vehicle load; vehicle maintenance; and the driver’s own behavior—can contribute in total to about a 45% reduction in the on-road fuel economy per driver (i.e., a fuel economy penalty), according to a new report by Michael Sivak and Brandon Schoettle at the University of Michigan Transportation Research Institute (UMTRI).
The report on Eco-driving also suggests that increased efforts be directed at increasing vehicle occupancy, which has dropped by 30% from 1960. That drop by itself, note Sivak and Schoettle, increased the energy intensity of driving per occupant by about 30%.
Average on-road fuel economy in the US for all vehicles in 2008 was 17.4 mpg US (13.5 L/100km); in 1923, the average was 14.0 mpg (16.8 L/100km). Driving a light-duty vehicle in the US currently is more energy intensive than flying, not to mention using a bus or a train (all at current average loads).
How can we improve on this performance? This report reviews how eco-driving enables drivers to maximize the on-road fuel economy of vehicles. In this report, eco-driving is used in its broadest sense: Eco-driving includes those strategic decisions (e.g., vehicle selection and maintenance), tactical decisions (e.g., route selection), and operational decisions (e.g., driver behavior) that improve vehicle fuel economy.—Sivak and Schoettle
Factors related to vehicle maintenance that impact fuel economy include engine tuning, tire selection and maintenance, and weight of engine oil. Tactical decision for drivers include:
- Selection of road type (including speed limit and patterns of acceleration and deceleration);
- Selection of grade profile;
- Dealing with congestion;
- Weight (i.e., loading). (On a related note, the average adult in the US in 2002 was about 24 pounds heavier than in 1960, resulting in a reduction in fuel economy of up to about 0.5%.)
Operational decision (driver behavior) that affect fuel economy include:
- Use of cruise control;
- Use of air conditioner; and
- Aggressivity of driving.
|Summary of effects of factors influencing vehicle fuel economy|
other than vehicle selection and configuration
|Tires with 25% higher rolling resistance||3–5%|
|Tires under inflated by 5 psi||1.5%|
|Improper engine oil||1–2%|
|Tactical||Route selection: road type||variable|
|Route selection: grade profile||15–20%|
|Route selection: congestion||2-–40%|
|Carrying extra 100 pounds||≤2%|
|Driving at very high speeds||30%|
|Not using cruise control||7% (while at highway speeds)|
|Using air conditioner||5–25%|
As an example, Sivak and Schoettle calculated that a car that nominally gets 36 mpg will experience a reduction to 19.8 mpg in actual fuel economy (a reduction of 45%) as a result of disregarding all eco-driving practices.
The research was supported by Sustainable Worldwide Transportation. The current members of this research consortium are Aramco Services, Autoliv Electronics, Bosch, China FAW Group, FIA Foundation for the Automobile and Society, General Motors, Honda R&D Americas, Michelin Americas Research, Meritor WABCO, Nissan Technical Center North America, Renault, and Toyota Motor Engineering and Manufacturing North America.
Michael Sivak and Brandon Schoettle (2011) Eco-driving: strategic, tactical, and operational decisions of the driver that improve vehicle fuel economy (UMTRI-2011-34)
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