Compatibility Standard Will Do Double Duty

Energy Bill Mandate for Vehicle Compatibility Will Improve Safety and Fuel Economy at Same Time

Posted:  6/12/2007

The SUV loophole in the original CAFE program contributed to the increase in market share of larger, heavier vehicles.  The market share of light trucks has tripled since 1976, and the difference in weight between a typical passenger car and a typical light truck has increased tenfold.  Compatibility, or how two vehicles interact in a crash, is based on several characteristics of vehicles.  Some of these characteristics also influence fuel economy such as weight and size.

Lack of Vehicle Compatibility Is Deadly

  • In a two-vehicle crash, the high bumper, stiff frame and steel-panel construction of SUVs can override crash protections of other vehicles, making them dangerous to others.
  • In frontal collisions between a car and SUV, the car driver is 4.3 times more likely to die than the SUV driver.
  • SUVs are also more than twice as lethal as cars in side-impact crashes with cars.
  • Very stiff front ends can also diminish a vehicle’s ability to protect its own occupants, because they fail to sufficiently absorb crash forces.

Vehicle Characteristics and Compatibility

  • The vehicle attributes that most influence compatibility are: size, weight, geometry and stiffness.
  • The perception that being in a bigger, heavier vehicle is safer is not supported by research.

Improved Design Could Improve Fuel Economy and Compatibility

  • A compatibility standard will encourage fewer gas-guzzling giants, more crossovers, and increased use of advanced materials.
  • Crossover vehicles, with unibody construction and a lower bumper have better fuel economy, less rollover risk, and are less harmful to occupants of other vehicles.
  • Use of advanced materials can reduce weight, improve fuel economy, and maintain size to retain a range of functionality.

A Powerful Answer to Major Fuel Economy and Safety Myths

  • Opponents of improved CAFE standards often argue that the cheapest, easiest way to improve fuel economy is through reducing weight, which allegedly has a negative impact on safety.  This never happened: only 15 percent of fuel economy gains in the late 70s and early 80s were from reduced weight, and then weight was only taken out of the heaviest vehicles.
  • Reducing weight in heavier vehicles would be beneficial for safety, and the heaviest vehicles have the most fuel economy benefit from reduced weight.
  • The 1997 study by National Highway Traffic Safety Administration researcher Charles Kahane suggests that in car-to-car or light truck-to-light truck collisions, the fatality risk is lower if weight in both vehicles is reduced.
  • Work by Hans Joksch in 1998 found that greater variability of weight is harmful, so reducing the weight of the heaviest vehicles would improve safety.

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