To help us provide you with free impartial advice, we may earn a commission if you buy through links on our site. Learn more

How autonomous emergency braking in cars can save lives


In the old days, active safety was provided by the horse you rode. Any hazard missed by the rider would be spotted by the equine radar system and you’d both come to a halt.

It’s taken a while, but this automatic braking function is now available on a growing number of cars, and not just the posh ones either. Order a new Ford Focus with the optional Driver Assistance Pack and it’ll come with a bulky lump of plastic ahead of the rear view mirror that hides a laser. This continuously scans the road ahead and if it spies a stopped car you haven’t, it’ll send a swift warning to hit the brakes and you’ll come to a complete stop.

Ford Focus Forward Alert

The Focus device is one of the simpler forms of what we’re being encouraged to call AEB, or autonomous emergency braking, and it’s the next big thing in car safety.

“We predict it’ll go across the board, like ESC,” says Colin Grover, project engineer at automotive research centre Thatcham. The Berkshire-based test-centre has already been heavily influential in raising the profile of ESC, aka electronic stability control, which is to become mandatory on all new cars sold in Europe.

Now Thatcham is applying the same rigorous programme of testing and rating to autonomous braking, and you wouldn’t bet against being made a legal requirement for all cars in the future too.

In studies carried out with Loughborough University into the potential benefits, Thatcham calculated that if every car was equipped, 64 deaths and 650 serious injuries could be prevented every year in the UK, with 2,700 fewer pedestrian casualties too. Because, as well as spotting cars, the systems are now being trained to identify people in the road.

“Humans are pretty unique in their shape. We’ve got a round head on top of a square-ish body – we’re pretty easy to identify,” says Grover.

A good example is Volvo’s version, which starts with the same laser as the Ford Focus. This lidar (light detection and ranging) keeps its beady eye out for slowing or stopped cars and works up to 19mph (30km/h), but in full spec it’s also linked to a camera and two radar sensors that’ll work at higher speed too.

Together they’ve been programmed to not only identify cars, but also pedestrians. And in the future Volvo says the system will recognise runaway animals too.

Volvo animal detection

They’re not cheap to buy, for example to spec the emergency braking on the Focus costs £1,000 on the Zetec model, but it also comes bundled in with other safety equipment using the same sensors, including on the Focus a system whereby the camera will snap road signs to display the current speed limit on the dash.

Most commonly, however, they’re linked to the autonomous (or adaptive) cruise control. This radar system keeps a set distance to the car in front and has been around for over 10 years, with even high-spec versions of the Nissan Primera having it in 2002.

It was Honda who first had the confidence to say, right, we know this system can automatically brake the car, so let it emergency brake too. First sold in the UK with the CR-V SUV in 2006, it was described as brake mitigation, which meant it wouldn’t bring the car to complete stop. It was enough to dramatically reduce the size of the impact, but the now-awake driver was expected to supply the rest. It also introduced the now-common idea of preparing for a crash, here tensioning the seat belts.

Honda CR-V

The latest AEB technology will automatically brake to a stop if the series of warning alarms doesn’t alert the driver. Audi’s top-spec system, Pre-Sense Plus, features a camera in the rear of the car as well so it knows it’s safe to do a full-on emergency stop from any speed without risk of another car ploughing into the back.

Of course the future will bring further refinements, spurred on by the fact that the laser, radar and camera tech is getting useably cheap. Toyota has a system that sticks another couple of sensors on the front corners of the car, pointing outward to check for passing traffic at junctions.

Linking with the satnav is another rich area of research, with US in-car entertainment expert Alpine experimenting with a system called Top View that combines cameras with map technology to assess, for example, if a car is going too fast into the next bend.

Of course once you link ultra-fast, highly intelligent sensors with mapping, then driverless cars move closer to reality. In fact, this exactly what Google is trying to prove is possible with its sensor-festooned Toyota Prius hybrids testing in California. For most people though, the price of a standard emergency braking system will be repaid double the first time a warning beep snaps out of their reverie and alerts them to a stopped car ahead.

Read more