Car safety features explained

When browsing a new car's options list, it's much easier to understand optional extras that improve comfort and convenience than 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. 

What tech a given car gets depends on its age and where it sits in the model range. Higher-end models will often have 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. Some features must be switched on automatically 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.

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 applies 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's effectively mandatory because 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 the manufacturer chooses, EU law requires it to activate automatically each time you start your car and not 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 map data update in a while, it may have incorrect speed limit information built in.

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

If your car’s ISA system is set to automatically limit your speed, you can temporarily deactivate it by pressing hard on the accelerator, but it will reactivate every time you start your car.

Electronic stability control

Electronic stability control (ESC) automatically applies the brakes to individual wheels when it detects the car is about to lose control.

Manufacturers have been required to install it in all new cars since 2014. 

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. 

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 cruise control systems, and also set your preferred following distance to vehicles in front of you. 

If you’re catching up to a car driving slower than your target speed, the system will automatically reduce your vehicle’s speed to match and maintain the distance you 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 your first advanced 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 good all-round visibility to be among the first aims of any new car design. 

However, modern cars tend to have poorer visibility than many older models because of oversized pillars, though they largely compensate with cameras and/or proximity sensors that 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 contributes to 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.

Some manufacturers are now adding occupancy monitors that will alert you if you've left the car with someone in the back seat.

Attention monitoring systems

These systems monitor the driver's responses, looking for signs of fatigue. 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 became 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 vehicles beside them. This is normally done via a light in the door mirror, often backed up by an audible alert if the driver doesn't see it and tries to change lanes.

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 headlamp beam direction directly to the steering.

The most advanced systems not only let the headlamps turn with the wheels, but also use cameras to detect cars ahead. If the system detects them, it automatically adjusts the headlight beam 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 pressure and send a signal to the driver via a dashboard warning.

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 the car’s detailed category scoring, 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. Seat sensors also detect 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. Euro NCAP tests front head restraints 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 because they stay in the correct position if the seat moves. 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 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 an imminent crash, 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 may not fully protect the passenger in a crash. Three-point Isofix systems have two lower anchorages, and a third anchor point which can be a ‘top tether’ or a support leg. 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 give the safest child car seats our Best Buy recommendation. Find out which ones you should consider.

Pedestrian protection

If the worst happens and your car collides with a person, whether a pedestrian or cyclist, it should be designed to mitigate 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 used a variety of technologies, including pop-up bonnets and deformable bumpers, to reduce impact severity.

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