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driving concerns

I saw that rear automatic emergency braking systems failed much of the time in recent tests, but how does front emergency braking fare? Does any of this safety tech reduce crashes in the real world? – Chris

Systems designed to hit the brakes if something – or someone – is in your car’s path can prevent some serious crashes – but they don’t always work like they’re supposed to.

“Transport Canada and other studies have shown a great potential of [automatic emergency braking] systems to reduce the severity of certain collisions or to avoid them to the maximum extent possible,” Sau Sau Liu, a spokeswoman for Transport Canada, said in an e-mail. “However, in certain select circumstances, these systems may not reliably detect objects in the vehicle’s path.”

AEB uses sensors and cameras to detect objects in the path of your car and, if you don’t stop after a warning, it applies the brakes automatically. Some AEB systems are designed to detect – and stop for – pedestrians.

But tests show they might struggle or fail entirely in situations that include higher speeds, winter weather, the dark or when faced with cross traffic or left-turning vehicles.

For instance, in Transport Canada’s winter tests of front AEB systems, three of the five vehicles tested didn’t give a collision warning when their sensors were covered in ice.

In tests where an inflated target was shaped like a child and wearing winter clothes and a backpack, one of the four vehicles hit the child at 20 kilometres an hour.

In tests of front AEB systems by the American Automobile Association (AAA), the system prevented a collision with the car ahead at 30 miles an hour (48 kilometres an hour) 85 per cent of the time.

When there was a crash, the AEB reduced the speed of impact by 86 per cent.

At 40 miles an hour (64 kilometres an hour), AEB prevented a crash 30 per cent of the time – and reduced the impact speed in crashes by 63 per cent.

But in AAA tests where AEB had to detect and stop for a car turning left in front of the test vehicle or for a car coming from the side, AEB didn’t issue a warning or slow down – there was a crash 100 per cent of the time.

“[Safety systems] all have their issues and I think the message universally is that, as a driver, you shouldn’t expect them to replace good habits,” said Austin Shivers, AAA technical engineer.

Avoiding crashes?

Of all the accident-avoidance tech on cars now, AEB has been shown to prevent the most crashes, said the U.S.-based Insurance Institute for Highway Safety (IIHS).

When comparing collision rates for cars with AEB to cars without it, front AEB has been found to cut front-to-rear crashes by half – although the systems weren’t as good at preventing crashes with large trucks and motorcycles as they were with cars.

Cars with rear AEB, rear-view cameras and parking sensors had 78-per-cent fewer backup crashes than cars without those technologies.

For comparison, blind-spot warnings reduced lane-change crashes by just 14 per cent.

“We encourage people to get [AEB] if they purchase a car,” said David Aylor, IIHS vice-president of active safety testing. “I think if the technology matures, all the vehicles will do well [in testing].”

While AEB isn’t regulated yet in the United States or Canada, both countries have proposed requiring it on new vehicles. There are no target dates for when that could happen.

If your car has emergency braking or any other crash-avoidance system, you’re still responsible for any crash that happens if the system fails, said the Insurance Bureau of Canada (IBC).

“These features assist a driver; … they do not replace a driver,” Rob de Pruis, IBC’s national director of consumer and industry relations, said in an e-mail.

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