Has The Time Come For Rear-Crash Testing?

Edward Niedermeyer
by Edward Niedermeyer

Although cars are becoming more and more safe with every new generation, auto safety nuts are forever finding new ways to make cars seem scary. In some cases, the rush to create new crash test standards can create as many problems as it solves (see roof-crush standards), but in others you wonder why certain standards aren’t tested on every vehicle. One case that falls into the latter category: rear-crash tests. No government requires rear-crash testing, but in the wake of several accidents, Germany’s AutoBild magazine decided to look into what exactly happens when a car is hit from behind at 64 km/h… and the results are not encouraging.

AutoBild and DEKRA bought two cars to test for rear-crashworthiness, a Toyota iQ to represent small cars and a Renault Grand Scenic to represent compact MPVs. And these two vehicles were not necessarily chosen at random either: both received 5-star ratings from the European NCAP crash test program, which test for front and side impacts, but has no full rear crash test. Also, both offer very little in the way of rear crumple zones. Compact-based MPVs, particularly those with third rows, offer between 21 cm between the rear headrest and the rear hatch (on the tested Renault) and six cm (Ford Grand C-Max), measurements that suggest problems for third-row, rear-crash safety.

Sure enough, the results were not good. The Renault was placed about four feet behind a station wagon, filled with seven dummies, and hit at about 40 MPH by a Mercedes ML. The SUV dove some 30 centimeters into the rear of the car, and delivered huge amounts of impact to the rear-seat passengers. According to the attending doctor, three of the Renault’s passengers received eight separate different impacts that exceeded safety standards. Particularly bad were head, neck and torso impacts for third-row passengers, who could expect brain injury and hemorrhaging, vertebrae and intervertebral disc fractures, and rib fractures with the possibility of organ penetration. Not great for a 40 MPH crash in a five-star car.

Similarly, the iQ was hit at a lower speed (32 MPH) and by a smaller vehicle (an Opel Vectra), but the rear-seat passenger still would have suffered serious injuries, including vertebrae and pelvis and leg bone fractures, as thigh, torso and neck impacts again exceeded established limits. Even front-seat passengers saw impacts that nearly reached the limits. Meanwhile, the rear-seat occupant would likely be unconscious and trapped in the back of the vehicle, requiring removal of a passenger seat or cutting the roof to rescue them. Even the rear airbag appeared to not fire properly in the rear-impact test.

Obviously these were only two tests of very different vehicles under unique circumstances, but the results do seem to indicate that some kind of rear-crash test standard should be looked into. After all, front-impacts are ultimately the driver’s responsibility, while rear-impacts are unavoidable with “active safety” measures (aka defensive driving). AutoBild’s conclusion is that the NCAP program should start testing rear impacts, and we can certainly see the benefit to such testing. And with more European-style compact MPVs coming to the US (Ford C-Max, Buick-badged Opel Meriva/Zafira), this issue is worth discussing the US-market context as well. This is not to say that any type of vehicle is fundamentally unsafe, but AutoBild and DEKRA’s research definitely points towards an important opportunity for greater research.

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  • Herb Herb on Feb 22, 2011

    @Perisoft, regarding weight: The curb weight (ready-to-drive) of an SL450 (1973) was 3,160 pounds (1,580 kg), not 4,500. The curb weight of an S class (W126) in the eighties was between 3,140 pounds (260SE, 300SE) and 3,600 pounds (560SE). Theses cars were massive and safe, because they had been designed with safety concerns in mind. They were very safe, because engineers could not rely on an airbags. Plain old SRS had to do. Now look at the curb weight of contemporary cars. BTW: I'd rather DIAF in a hatch or a station wagon, than driving around with a semitrailer or silly sedan, just to be on the safe side should a rear-ender occur *). *) Already had one, in a Fiat Panda (http://en.wikipedia.org/wiki/File:1997_Fiat_Panda.JPG), curb weight 1,400 to 1,600 pounds, although not at 32 mph.

  • Voyager Voyager on Aug 27, 2011

    Yes, it's about time authorities looked into this matter. Rear-end collisions are a far more frequent occurrence than head-on collisions. An intriguing thought is that car makers themselves are opposed to do this particular sort of crash testing. I asked NCAP if it is planning to do additional testing in the near future. Better rear-end crash protection by using another layout has been formally proposed by me to a consortium of car makers and automotive suppliers. I am curious what they will do with this. Ignore? Embrace? Marginalize?

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