关于汽车安全性能的比较

The IIHS(Insurance Institute for Highway Safety) is a good source for data on the real world crash performance of new vehicles. The US Department of Transportation's National Highway Traffic Safety Administration (NHTSA) also requires that car manufacturers conduct slightly different tests, but vehicles that perform well in one set of tests generally do well in the other.

The results of IIHS crash tests are easy to search online (http://www.iihs.org/ratings/default.aspx) so I have collected the results for a variety of small and mid-size European and Japanese cars in a single table.

The cars are sorted in order of fuel economy in city driving (MPG = miles per gallon.) Results for the "Side Impact" test represent a crash where an SUV hits the driver's side of the vehicle. Results for the "Front Offset" test represent a head-on collision with another vehicle of the same mass, with 40% overlap between the two vehicles.

The results are color-coded to a four-step scale, according to the possibility of injury from excessive deceleration of the driver/passenger, or collapse of the vehicle body, causing injury. The deceleration results are specified by "head/neck","chest","leg/pelvis" etc.

Green - Good
Yellow - Acceptable
Orange - Marginal
Red - Poor

Injuries can not be predicted perfectly (it's really the statistical probability of injury.) But in general, Good and Acceptable results indicate that no injury, or only minor injuries are likley. Marginal and Poor results indicate that moderate or severe injuries may occur.



 To summarize the results for these vehicles with two points:
1) There is no evidence that the heavier vehicles are safer (in fact, the heaver BMW 5-Series, and Mercedes C and E-Class perform the worst in side impact)
2) Safety should not be a major reason for choosing to buy (or not buy) any of these vehicles. The crash results for all of these vehicles are quite similar.

It may seem suprising that lighter vehicles can be as safe (or safer than) heavier vehicles, and that vehicles with a good reputation for safety (like Volvo) don't always perform better than others. However, the truth is that vehicle safety is very dependent on good design, and unless there is a very big difference in mass (like between a Hummer and a Smart), design will be the most important thing. The European and Japanese manufacturers have done a very good job in the last 10 years of designing vehicles that absorb energy in the front crush zone without allowing the cabin area to be damaged. For side impact, these companies have improved the strength of the body, and use air bags and collapsable trim pieces to absorb the energy and reduce the chance of injury. As a result of these design changes, within any size class, vehicles from Honda, Audi, Toyota, BMW, Volkswagon, Mercedes, Nissan, Volvo, etc all have similar safety performance.

One final comment about the use of recycled materials and safety. Nearly all vehicle bodies today are made of steel (with the expection of specialty vehicles like the Audi A8, or Lotus Elan which use aluminum or carbon fiber) and the crash performance will not be affected by the use of recycled steel content. In fact, all these vehicles use steel from the same suppliers, and all the steel will contain some recycled steel. Some companies may advertise the use of recycled plastics in the interior, but this will not have any effect on safety. In fact, the use of recycled material should be considered a positive thing for the environment!