Car safety features explained

Browsing the options list of a new car, it's much easier to understand optional extras that improve comfort and convenience than it is to know whether optional safety extras are worth investing in.

While it’s never nice to think about the worst that might happen on the road, ensuring your car has the right safety features can make all the difference in an accident or avoiding one completely. This is thanks to developments in safety tech and more stringent testing and legislation that obligates manufacturers to include more and more safety features. 

What sort of tech a given car gets depends on the car’s age, and where in the model range it sits. Higher-end models will often come with more kit as standard, while the cheapest models may make them optional extras. 

Vehicle safety kit can be classified in two ways: ‘active’, which will intervene before an accident to improve safety; and ‘passive’, which operates to protect passengers once a crash has happened.

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What is ADAS? Active safety features explained

Active safety features are also sometimes known as ADAS (Advanced Driver Assistance Systems) and can often be customised from within a car’s touchscreen interface, if it has one. There are some features that must be switched on every time the car starts (such as speed limit warnings), but others are optional and can be configured to your liking.

It’s worth noting that while some active safety features are mandatory on all new cars, you aren’t legally obliged to have them switched on all the time and, ultimately, you are still responsible for your car even if it’s being controlled by ADAS at the time of an accident.

We also checked with the Association of British Insurers (ABI) about whether turning off such features would invalidate your insurance in the event of an accident. The short answer is: no. 

The ABI said: 'There are a range of advanced driver assistance systems (ADAS) making UK roads safer, including Intelligent Speed Assistance and Emergency Lane Keep technology. While it is best practice to keep these systems switched on to promote safe driving habits, you should still be covered by your motor insurer if you decide to switch it off and are later involved in an accident.'

Of course, you should check with your specific insurer if you’re concerned.

Watch our video explaining how the latest active safety technology works and why it's worth having on your new car.

Intelligent speed assistance

Intelligent speed assistance (ISA) detects the speed limit on roads using a combination of GPS and cameras that are designed to recognise speed signs. It then uses this information to either limit your speed or produce a visual or audible warning when you go over the limit.

ISA became a legal requirement for all new car models that were introduced in the EU after July 2022. From 7 July 2024, this law was introduced to all new cars sold in the EU and Northern Ireland regardless of when they were first launched. While this technology isn’t mandatory in England, Scotland or Wales, it is effectively mandatory due to the fact that manufacturers prefer to keep their cars as similar as possible no matter where they are sold. 

Manufacturers can fit cars with four different ISA systems:

• Sound warnings
• Vibration warnings
• Feedback through the accelerator pedal
• Direct speed control

Regardless of the system chosen by the manufacturer, EU law states that it must activate automatically each time you start your car and can’t be permanently deactivated.

While keeping drivers within the speed limit is obviously a good thing, in our car-testing experience we have found that camera-based speed-sign recognition can be very patchy, while GPS-based speed limit systems are only as accurate as the speed limit data that’s available; if your car hasn’t had a software update in a while it may have incorrect speed limit information built in.

Ultimately, the driver is still responsible for ensuring the car is travelling at speeds appropriate for the road and traffic conditions, as well as being within the speed limit.

If your car’s ISA system is set to automatically limit the speed you travel at, you'll be able to temporarily deactivate it by pressing hard on the accelerator, but it will be reactivated every time you start your car.

Electronic stability control

Electronic stability control (ESC) is software that can automatically reduce engine power and, depending on the individual system fitted, operate individual brakes, should it detect the car is about to lose stability or is at risk of a skid.

Independent studies have shown that ESC could prevent up to a third of all road accidents. It’s such an important development that manufacturers have been required to install it in all new cars since 2014. 

Other acronyms used by manufacturers include ASC, DSC, DTSC, ESP, ESP+, VDC, VSA and VSC. Each may have a subtly different method of operation, but all operate to keep the car on its intended path, should the wheels be at risk of losing grip due to slippery conditions or the driver's inputs.

Autonomous Emergency Braking

Autonomous Emergency Braking (AEB) reduces the risk of a collision with another vehicle, pedestrians and cyclists. Previously manufacturers had the option of installing such a system, but now all cars manufactured since July 2024 must have some form of AEB (like speed assist, this is EU law, but will very likely be followed by all manufacturers in the UK). 

Autonomous braking systems use a variety of sensors and cameras to monitor the road ahead. AEB will audibly alert the driver to an impending collision.

If the driver doesn't take any action, the AEB system will automatically perform an emergency stop to reduce the effects of the collision. At lower speeds, many automatic braking systems can prevent an accident altogether. 

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Adaptive/intelligent cruise control

Adaptive cruise control (sometimes known as intelligent cruise control or ICC) uses sensors to detect how close you are to the car in front. Typically, you can set your target speed as with basic other cruise control systems, and also set your preferred following distance to vehicles in front of you. 

If you’re catching up with a car that's driving slower than your target speed, the system will automatically reduce your vehicle’s speed to match and keep to the distance you have set (if possible). If the car moves out of the way, or you switch lanes, adaptive cruise control will accelerate back up to the pre-set cruising speed. Some more advanced models will also avoid undertaking slower moving cars in the outer lanes and work in slow-moving traffic, bringing the car to a standstill before automatically setting off again.

You can typically override anything your adaptive cruise control is doing by using the accelerator (in many cars this will pause the system until you release the throttle) or brakes (this will cancel the adaptive cruise control entirely and require you to turn it back on).

These systems can be fiddly to set up the first time you use them, so it’s worth reading the manual before embarking on your first advance cruise control-assisted journey so you don’t spend too much time staring down at the controls. 

Lane-keeping technology

Basic lane-keeping systems simply warn the driver if they let the car stray too close to the edge of their lane on the motorway without indicating. This is done either through an audible warning or through vibrating the steering wheel. 

More advanced systems known as Lane Keep Assist (LKA) will automatically make steering adjustments to keep you within lane, though most will stop working after a set period of time if they detect the driver is not holding the steering wheel or making any attempt to keep the car within its lane themselves.

Emergency Lane Keeping (ELK) kicks into action when a car is leaving a lane and is on a collision course with another vehicle and was made mandatory on all new vehicles sold in the EU after July 2024. 

On some models, active lane keeping can be used in conjunction with adaptive cruise control. This allows the car to steer itself to stay within the lane markings on a motorway, although you must maintain full attention and keep both hands on the steering wheel, or the system will deactivate and hand control back to the driver. 

Visibility aids

You would expect that good all-round visibility is among the first aims of any new car design. Unfortunately, with modern cars there is always a conflict between the need to strengthen the cabin to withstand serious crashes and the need to see out from the driver's seat.

This means that modern cars tend to have poorer visibility thanks to oversized pillars, though they largely compensate with cameras and/or proximity sensors to alert the driver to obstacles they might otherwise miss.

The most advanced systems utilise an array of hidden cameras to stitch together a 'top-down' view of the car, which can make manoeuvring into the tightest of parking spots a doddle, but you’ll also find some cars that activate blind-spot cameras within the instrument cluster when you indicate, to give you a better view of anyone or anything below the window line; this is particularly useful in large SUVs. 

Smart seatbelt reminder

As a nation we’re pretty good at buckling up, but not using seatbelts is a contributing factor in 21% of car occupant fatalities (according to UK government statistics from 2022). The best systems don’t just remind the driver to buckle up: they sense which seats are occupied and alert the driver if any other belts haven’t been fastened.

Attention monitoring systems

These systems monitor the driver's responses, looking for signs that might indicate tiredness. They vary between manufacturers. Some sound an alarm; others vibrate the seat or give visual warnings to alert the driver that it's time to take a break. This was made mandatory along with intelligent speed assist in new cars sold after July 2024.

Blind spot warning systems

Blind spot warning systems can reduce the likelihood of an accident when changing lanes by alerting drivers to unseen adjacent vehicles. This is normally done via a light in the door mirror, which is often backed up by an audible alert should the driver not see it and make an attempt to change lane.

Similarly, some cars feature ‘cyclist dooring prevention’, which sounds an alarm if it detects you're opening your door into a passing cyclist. 

Active headlights

Basic active headlight systems have additional lights that come on to the left or right for cornering, lighting up the bend as you go. More sophisticated systems have active beam control, which links the direction of the head lamp beam directly to the steering.

The most advanced systems not only allow the head lamps to turn as the wheels do, but also use cameras to detect cars ahead. If the system senses them, it adjusts the headlight beam automatically to provide maximum illumination without dazzling other road users.

Tyre-pressure monitoring systems

Having under or over-inflated tyres can upset the car's handling and lead to an accident. Tyre-pressure monitoring systems (TPMS) warn of incorrect tyre pressures, helping you maintain them at the correct setting.

There are two basic types: 'direct' and 'indirect' pressure monitoring. Direct tyre pressure monitoring involves the use of a sensor inside each tyre to measure the pressure and send a signal to the driver via a warning on the dashboard.

Indirect tyre pressure monitoring systems do not have sensors. Instead they use the anti-lock brake system (ABS) sensors to monitor wheel speed. If the system senses a change in a wheel speed relative to the other wheels, it calculates that the rolling circumference must have changed and assumes this is due to a change in tyre pressure.

Passive safety features explained

A strong body shell

The starting point for vehicle safety. A well-designed car body shell resists and dissipates crash forces well and provides better protection for those in the cabin. Look for cars with a good Euro NCAP crash-test score. Check out the car’s detailed category scoring and not just the headline star rating.

Dual-stage airbags

Airbags can make the difference between an occupant receiving minor injuries and serious injury or death in a 40mph head-on crash. Sensors in the car monitor deceleration rates and then fire the airbags to cushion any impact between the occupant and the car's interior.

Dual-stage airbags have sensors that trigger different responses for crashes of different severity. For example, they inflate less rapidly in lower severity impacts, reducing the chance of airbag-related injuries, while still cushioning the impact. Sensors in the seat also account for how far forward the passenger is sitting, and can inflate the airbag accordingly, to provide the best protection.

Good head restraints

Poorly designed or adjusted head restraints account for many whiplash injuries, which usually occur if you are shunted from behind.

Make sure that a car’s head restraints can be raised high enough to suit drivers and passengers of all heights – the top of the head restraint should sit level with the top of the person’s head, and the head should be no more than an inch away from the restraint when the occupant is sitting comfortably for it to be effective. Front head restraints are tested by Euro NCAP to check their resistance to whiplash injury.

Seat-mounted side airbags

These help protect the pelvis, chest and abdomen in a side-on crash. Seat-mounted side airbags are preferable to door-mounted airbags as they stay in the correct position should the seat move. Side airbags are normally fitted as standard for front-seat passengers but may only be offered as an option in the rear.

Side curtain airbags

These usually drop down from the roof lining above the windows to protect the heads of front and rear passengers in the event of a side-on crash. If you're buying a seven seat car such as an MPV, it's worth checking that the curtain airbags extend to the third row, as this varies between manufacturers.

Knee airbags

Historically, advances in car safety have focused on crash survival, but now manufacturers pay attention to how the deformation of a car’s interior in a collision can leave passengers with life-changing injuries – particularly to the legs of front-seat occupants.

The development of the knee airbag means drivers would be cushioned from immovable objects such as the steering column and the leading edge of the dashboard, preventing injury to their lower limbs and pelvis. It’s just one of the many developments that could mean the difference between walking away from an accident and being stretchered out.

Pre-tensioned and load-limited seatbelts

Seatbelt pre-tensioners take up any slack in the belt when they detect a crash is imminent, keeping you fixed in your seat. Load limiters, on the other hand, prevent injury by allowing the belt to stretch slightly as the crash takes place so that not too much force is placed on the passenger’s body, particularly their ribcage.

Isofix child seat mounts

Isofix is a system for fitting child seats that uses mounting points built into the car seats, rather than the seatbelt. It has become the accepted standard for fitting child car seats, with nearly all manufacturers offering it, at least as an option.

The main benefit is that they make the seat easier to install, so there's less risk of getting it wrong. An incorrectly installed child car seat means it may not give full protection to the passenger in a crash. Three-point Isofix systems come with two lower anchorages, and a third anchor point which can be a ‘top tether’ or a support legs. The type you choose will depend on your car – a car with an underfloor storage cubby is unsuitable for a child seat with a support leg, for instance.

We only award Best Buys to the safest child car seats. Find out which ones you should consider.

Pedestrian protection

Should the worst happen and your car does collide with a person, be it a pedestrian or cyclist, your car should be designed to mitigate the worst of the impact. Euro NCAP tests all its crash-test cars for pedestrian protection and provides a clear rating for both the protection of children and adults hit by the car under test. 

The key behind this is vehicle design that decreases the likelihood of hitting ‘hard points’ such as the A-pillars or engine block. Manufacturers have employed a variety of different technologies, including pop-up bonnets and deformable bumpers, to decrease the severity of an impact.

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