THE CAR EXPERTCar finance and buying advice

There is a big push at the moment to have all new cars fitted with autonomous emergency braking (AEB) systems, with several big-name road safety organisations claiming that these auto-braking systems could reduce thousands of crashes and save many lives each year. But what exactly are they talking about?

What is autonomous emergency braking?

Simply put, an autonomous emergency braking system detects that you are approaching a stationary or slow-moving object in front and provides a collision warning. If the driver does not respond quickly enough, the AEB system can apply the brakes to slow or stop the car on its own. Newer systems can even detect pedestrians and cyclists, rather than just other vehicles.

AEB systems are sometimes called city braking systems (or similar), as they are usually most effective at speeds under 20mph where they can usually avoid an impact altogether. At higher speeds, the system may not be able to prevent an accident altogether, but it can significantly reduce the impact speed and therefore reduce the damage done to both car and occupants.

How does an AEB system work?

The system is based around a laser or camera (or both, or multiples of each), which scans the road ahead as you are driving. If it detects a stationary or slow-moving object up ahead, the system will give off a warning – usually beeping and/or lights and/or a message. Some systems will also start preparing the car for braking by bringing the brake pads right up close to the brake disc, so that when the brake is activated they are applied instantly – it saves milliseconds, but every faction is important.

If the driver does not respond within a certain time limit, the system will automatically start applying the brakes (and cutting engine power) irrespective of what the driver is doing.  If the car is moving towards a stationary object at less than 20mph at the time, the system can usually avoid an impact altogether. At speeds above 20mph, the car may well not stop entirely before an impact occurs, but the impact speed will be greatly reduced.  Some more sophisticated systems are able to operate at up to 140mph (although if you’re travelling towards a stationary object at that speed, it’s still going to be a big accident).

The AEB system is integrated into the car’s existing stability program (ESP) system (which has been a standard requirement in Europe for a number of years now). The ESP system can already control the brakes and accelerator with no input from the driver, so adding AEB does not require extensive modification of the car’s existing control systems – especially for new models where it is designed-in to begin with.

What is it like?

Seeing autonomous braking in action is definitely eye-opening. I first experienced an automatic braking system on an Audi A8 in Munich several years ago.  The car was able to follow the vehicle in front at over 100mph on an autobahn, and was able to come to a complete stop without me touching the brake pedal at all when the car in front slowed and stopped.

Low-speed AEB is equally impressive. When on a Mercedes-Benz training programme for the new C-Class (I worked for a Mercedes dealer at the time), we had to drive towards a large wooden wall at 30mph. The car started beeping but we were told to ignore it and maintain speed.  With no driver response, the car cut the accelerator input and applied maximum braking, pulling up centimetres from the wall every time.  Even at what seemed a low speed, the level of braking force was much more violent then a human driver would ever be likely to apply, even in an emergency.  But the wheels did not lock, meaning the driver could steer around the obstacle if necessary.

Why is it important?

UK car safety institute Thatcham Research says that a quarter of all car crashes are nose-to-tail impacts. AEB systems can reduce this number significantly, and even if an accident is unavoidable, the system can at least reduce the severity of the impact. At the very least, it could save you thousands in car insurance costs; and at the most, it could save lives and reduce serious injuries. Newer systems that can detect pedestrians and cyclists are even more advanced, and can reduce fatalities and injuries for vulnerable road users – even if the collision is not the driver’s fault.

There have also been many reports of insurance fraud with regards to whiplash from nose-to-tail impacts, and con artists engineering low-speed car accidents to claim on insurance. This obviously costs the rest of us money though increased insurance premiums.

Some insurance companies are offering reduced insurance premiums of up to 10% to vehicles with standard AEB systems.

How much does it cost?

There have been some somewhat misleading articles published over the last few days, implying that a basic AEB system costs as little as £37. Unfortunately, it’s not that simple. A basic kit of sensors might cost a manufacturer £37, but it has to be properly mounted to fit the car, integrated with the rest of the car’s systems and then extensively tested to make sure everything works properly. And that’s all expensive stuff.

WhatCar? highlights the Volkswagen Golf, which has AEB as standard on most models, to argue that all cars should be fitted with this technology. However, a basic AEB system is available as an option on several other models in the Volkswagen family, and it costs more than £200.  Assuming that VW applies the same profit margin as it does on other options, it’s costing them a lot more than £37 to fit.

For the AEB system to actually work, the car also has to have a number of other systems as well. Many of these systems are now standard, but they still have to be made to work with AEB, such as the ability to apply full braking pressure without the driver touching the brake pedal.

Many manufacturers offer AEB in conjunction with other safety systems. While AEB might be standard on most Volkswagen Golf models, the sister Audi A3 model range only offers AEB in conjunction with an adaptive cruise control system, meaning the cost starts at £575 depending on specification and other options.

So, in short, it’s not as cheap as some of the headlines suggest. However, even at a couple of hundred pounds, it’s still worthwhile.

So how soon will all cars have AEB?

The push to make automatic braking systems standard is only going to grow stronger. EuroNCAP, the independent crash-testing body, already gives higher scores to cars fitted with AEB systems. This has started to trigger a response from mainstream manufacturers to start fitting it as standard equipment.

Although the systems have been on sale for a number of years with several manufacturers, the uptake from customers when given the choice to buy AEB as an option has been very low – Thatcham suggests less than 2% of car buyers choose to pay for AEB when they have the choice. Why is this so?

Well, it’s probably twofold. Firstly, car buyers are notoriously reticent to pay extra for safety-related options. In recent history, safety features like airbags, anti-lock brakes and stability systems started off as options, as all struggled to find favour. Generally, customers would rather spend money on trinkets they can see, like a satnav or sunroof, than on a safety system that they hope they will never need. Dealers know this, so they don’t order stock with safety options since they know customers won’t want to pay for them.

Secondly, car salespeople are notoriously poor at explaining safety systems with anything like the same sort of zeal they apply to flogging overpriced car-cleaning crap or GAP insurance which earns them big commissions. And they are also incentivised to sell the cars they have in stock – and as just mentioned, dealers don’t order cars with safety options for stock…

Like seat belts, airbags and stability systems, there is no doubt that autonomous emergency braking systems will become standard equipment eventually. Virtually every new car that it launched now has it either as standard fitment or available as an option. If you are looking to buy a new car, it’s definitely worth having.