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Goddard Space Flight Center, Greenbelt, Maryland 20771

ENGINEERING COLLOQUIUM

Monday, April 7, 2008 / 3:30 PM, Building 3 Auditorium

Marc Ross

"Traffic Safety, Vehicle Mass, and the Laws of Physics"

ABSTRACT -- The potential to improve the fuel economy of light-duty road vehicles (LDVs) while also improving traffic safety is in dispute because of the widely held belief that lighter vehicles are, and must be, especially dangerous for their occupants. The relation of mass to risk is, however, not simple. Many midsize cars have safe records, as have some of the lightest cars like VW Jetta and Honda Civic. I highlight Jetta and Civic because they are rather safe even though their drivers are among the most aggressive, with high fractions of young males and of violations for speeding and alcohol. There are, however, other light cars like Chrysler Neon and Chevy Cavalier that are very dangerous for their occupants. Many believe it is a law of physics that lightweight vehicles are especially dangerous. I suspect instead it is a "law of economics" that the cheapest vehicles are dangerous. Evidence for this controversial claim: The striking inverse relation between used car prices and risk.

I will discuss three kinds of vehicle modifications being made or considered to reduce risk: 1) adding devices to improve control over vehicle motion, such as stability controls, 2) improving vehicle structure to enhance "interaction" in crashes, i.e. to increase the conversion of kinetic energy into deformations outside the passenger compartment, and 3) improving compatibility between light trucks and cars, by redesigning those trucks which are simply intended as car substitutes. Some in the industry have claimed that so much progress has already been made in "passive safety", that modifications like types (2) and (3) are no longer a priority. This claim of great progress is belied by the fact that total on-road fatalities have held roughly constant for many years at over 40,000 annually.

SPEAKER -- Marc Ross received his Ph.D. in physics from the University of Wisconsin (1952) and has been a professor in the Physics Department, University of Michigan, since 1963. He nominally retired, moving onto TIAA-CREF's payroll, in 2001. Since the mid-1970s, Prof. Ross’ research has involved analysis of energy use, its impacts on people and the environment, and the reduction of negative impacts through efficiency and conservation. Up to the mid-1980s his focus was industrial energy use. Since then he has focused on energy and automobiles. Much of his research concerns technologies to improve fuel economy. An important part of this has been creation and improvement of models of fuel use and emissions as they depend on driving. In recent years he has been studying relationships between traffic safety and vehicle design. Since lightweight vehicles would reduce greenhouse gas emissions and save oil, the main research issues are: What would their safety of light vehicles depend on? What design changes would enhance their safety?

His article, "Vehicle Design and the Physics of Traffic Safety", co-written with Deena Patel and Tom Wenzel, appeared in the January 2006 edition of Physics Today

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Engineering Colloquium home page: https://ecolloq.gsfc.nasa.gov