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I see TV ads for cars that brake automatically for pedestrians, but how well does this feature actually work? Can it detect children? I worry that people who have cars with this feature may not pay attention because they think their vehicle is doing it for them. – Suresh, Calgary

If you have a car with pedestrian detection, don't count on it to stop for pedestrians.

"Never rely on pedestrian detection systems to avoid a collision," said the American Automobile Association (AAA) in a report last fall. "These systems serve as a backup rather than a primary means of collision avoidance."

Most pedestrian detection systems use forward-facing cameras or radar – or both – to detect objects in front of your car. In systems that combine pedestrian detection with automatic braking, when the computer decides that you're about to hit something, it's supposed to warn you and apply the brakes.

The systems, which are increasingly getting offered as standard equipment, especially on higher-end cars, can stop some crashes – but they're not foolproof. On a test course with dummies, AAA evaluated pedestrian detection systems in a 2019 Chevrolet Malibu, 2019 Tesla Model 3, 2019 Honda Accord and 2019 Toyota Camry.

The systems worked best for adults standing still in front of a vehicle going 20 mph (32 km/h) during the day.

But, even then, they avoided hitting the dummy just 40 per cent of the time.

At night, the systems didn't work at all.

Won’t detect children?

What about a child darting out between two cars?

At 32 km/h, the cars hit the pedestrian, a moving model of a 7-year-old child, 89 per cent of the time. In about a quarter of the test runs where the car hit the child, the system was able to slow the car down by about 6 MPH (9.6 km/h), on average, before the crash.

The cars also fared poorly in other situations with adult pedestrians.

Faced with a dummy standing in the road immediately after a car turned right, all the cars hit the dummy.

When going 32 km/h, the cars hit dummies standing on the side of the road 80 per cent of the time.

At faster speeds – 30 mph (48 km/h) – the cars hit the pedestrians in every scenario.

In separate, simpler tests of midsized cars by the Insurance Institute for Highway Safety last year, 13 of 19 models either avoided pedestrians entirely or were able to reduce speeds significantly.

Generally, luxury cars fared better. The Audi A4, BMW 3 Series, Mercedes-Benz C-Class, Nissan Maxima, Subaru Outback and Volvo S60 earned top ratings.

But three cars – the 2019 Ford Fusion, 2019 Hyundai Sonata and 2019 Kia Optima – barely slowed down.

Believe the disclaimers

If your car has pedestrian detection, read the manual to see what it's designed to detect.

For all the cars tested in the AAA study, the owners manuals warned that pedestrian detection didn't work in all situations.

For instance, page 88 of the 2019 Tesla Model 3′s manual says, “Collision Avoidance features cannot always detect all objects, vehicles, bikes, or pedestrians, and you may experience unnecessary, inaccurate, invalid, or missed warnings for many reasons …”

For the Tesla, those reasons include sharp curves and poor visibility due to lousy weather.

The bottom line? The technology is getting better and could help prevent fatal crashes – in 2018, 332 pedestrians were killed by cars in Canada – but it’s no substitute for slowing down and paying attention.

Have a driving question? Send it to globedrive@globeandmail.com. Canada’s a big place, so let us know where you are so we can find the answer for your city and province.

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