Seven-seater Achilles' heel

Peter McKay April 29, 2011

ANCAP isn't planning a rear-impact test.

ANCAP isn't planning a rear-impact test.

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Seven-seat wagons are becoming must-have items for family car buyers these days, but is that third row of seats safe?

The truth is, nobody knows for sure, because the world's independent crash-test authorities don't really test them.

Existing crash tests focus on how well a car protects its occupants if it is hit from the side or the front or if it sideswipes a pole or tree.

To date, there is no test to see how well occupants of a third-row seat would fare if their car was hit from behind. At first glance, it appears there is little protection for them. The seats are usually placed where the cargo area is, so there's very little in the way of a buffer zone - or crumple zone, as the experts like to call them.

Also, curtain airbags, which protect an occupant's head in a side impact, don't extend to the third row of seats on some popular seven-seaters, including the Ford Territory and Holden Captiva.

A controversial crash test in Europe recently raised doubts about how well some cars protect occupants in the event of a rear-end impact.

Respected German automotive magazine AutoBild conducted two rear-end crash tests on a small city runabout and compact people-mover and found a high-speed accident could have dire consequences for passengers sitting in the rear seats.

AutoBild bought two cars for the tests - the small Toyota iQ and a Renault Grand Scenic family people-mover. The cars weren't singled out because they had shown weaknesses in previous crash-testing procedures.

In fact, both had earned five-star ratings in front and side impacts conducted under the European NCAP crash test program. But neither has any obvious rear crumple zones.

Compact people-movers, such as seven-seat soft-roaders, leave only a small cargo area forward of the rear hatch.

For the magazine test, the Renault, filled with seven dummies, was placed about one metre behind a station wagon and then hit at 64 kilometres an hour by a Mercedes ML, a heavy luxury off-roader. It penetrated some 30 centimetres into the rear of the Scenic, inflicting damage to the dummies in the rear seat.

A medical consultant judged that 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 haemorrhaging, vertebrae and intervertebral disc fractures and rib fractures with the possibility of organ penetration. It wasn't a great outcome for a five-star car hit from behind at a speed considered normal on many suburban roads.

The iQ (not sold in Australia) was hit at a lower speed (about 50km/h) and by a smaller, lighter passenger vehicle (an Opel Vectra). The medical consultant concluded that rear-seat passengers could have suffered serious injuries, including vertebrae, pelvic and leg-bone fractures, and thigh, torso and neck impacts exceeded established limits.

While the tests were unofficial and not conducted to the same stringent requirements as the European NCAP, the magazine concluded that the outcomes indicated some kind of rear-crash-test standard should be considered.

The Australasian New Car Assessment Program (ANCAP) does not have any plans to introduce a rear-impact crash test, although it will test for whiplash from next year.

Local safety experts are not convinced about the merits of adding rear-crash testing to the suite of passive safety obligations imposed on car makers.

ANCAP doesn't have local statistics but points to US figures showing 75 per cent of rear-enders happen at no faster than 16km/h - although they are the highest-represented crash type in the US.

''If ANCAP could develop a suitable protocol and find the funds - another $100,000 per test including one car - then we would possibly look into it,'' a spokesman says.

''But, that said, [crash-avoidance] technology is moving much faster than rear testing and improved rear design.'' ANCAP's ''road map'' for the future tests includes technology that will help mitigate the risk of this type of accident, including collision-avoidance systems, fatigue-warning systems and emergency brake assist.

Some systems, including Volvo's ''city safety'', can automatically bring a vehicle to a complete stop at lower speeds if the driver fails to respond to an emergency.

The senior manager of IAG's Insurance Research Centre, Robert McDonald, acknowledges that little cars such as the Toyota iQ mentioned in the AutoBild test can be very tight for rear-seat passengers ''and the passengers are placed fairly close to the window and tailgate''.

But McDonald points out that the impact scenario depicted in the magazine's article is quite rare, statistically.

''The test regimes followed by ANCAP and others try to cover the most statistically relevant injury modes,'' McDonald says.

''The most common injury type in rear-end collisions is whiplash.''

He says that the most potential for protecting rear-seat passengers will come via primary safety systems fitted to the following car.

''The forward-collision warning and mitigation systems that are starting to appear in cars such as the new BMW 5 Series do work and would be very effective in preventing this sort of situation,'' McDonald says.

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