Car safety features explainedby Daljinder Nagra
Safety is a crucial factor in choosing a new car. We explain the raft of safety features available so you can have confidence in your choice.
Put us to the test
Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.
- Get the Which? verdict from our independent experts
- Weigh up the pros and cons in an instant
- Go to town on the details with our full review
- Read our member reviews to see what they think
- Is it a Don’t Buy? It could be a dud, and a costly one too
- 682 Cars available
Browsing the options list of a new car, it can be tempting to choose high-end entertainment kit and technology and overlook advanced safety features.
And 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 a collision.
Thankfully, cars have never been safer, and manufacturers are continually developing vehicle technology to not only mitigate the effects of a collision but, in some cases, avoid one altogether.
Much of this technology is included as standard, but often varies from model to model. For instance, side airbags for rear passengers is often offered only as an optional extra, so it’s worth considering carefully.
Vehicle safety kit can be classified as ‘active’, which will take action before an accident to improve safety, and ‘passive’, which operates to protect passengers once a crash has happened.
Discover the cars we recommend by viewing our Best Buys.
Active safety features explained
Electronic stability control (ESC)
One of the most important developments in vehicle safety, ESC automatically reduces engine power and, depending on the individual system fitted, can operate individual brakes should it detect the car is about to lose stability or skid as the result of a driver’s inputs.
Independent studies have shown that ESC could prevent up to a third of all road accidents. It’s such an important development that manufacturers are now required by law to install ESC on all new cars.
This car safety feature is commonly known as ESC, but other acronyms used by manufacturers include ASC, DSC, DTSC, ESP, ESP+, VDC, VSA and VSC.
Automatic braking systems
One of the most important developments in car safety in recent years, automatic braking systems use a variety of sensors to detect any potential imminent collision. Individual systems vary between marques, but they will generally audibly alert the driver and then automatically apply the brakes should no action be taken. At lower speeds, many automatic braking systems can prevent an accident altogether.
Electronic brake-force distribution (EBD)
This development of anti-lock brakes (ABS) automatically distributes brake force between the wheels, helping to minimise stopping distances while bringing the car to a halt predictably and in a straight line.
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 haptic feedback (e.g. a vibrating steering wheel).
More advanced systems will automatically make steering adjustments to keep you within lane, though most will stop working after a couple of minutes if they detect the driver is not holding the steering wheel or making any attempt to keep the car within its lane themselves.
Many cars fitted with cruise control also come with a feature to prevent the car being driven above a pre-set speed. Speed-limiting devices can normally be set to any speed and will gently reduce engine power when it is reached. Many systems will deactivate if the driver floors the accelerator so they can still react to developing situations on the road.
Smart seatbelt reminder
As a nation we’re pretty good at buckling up, but not using seatbelts is still a major factor in road traffic injury statistics. 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.
Good visibility and/or 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 largely compensate with cameras and/or proximity sensors to alert the driver to obstacles they might otherwise miss.
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 backed up by an audible alert should the driver not see it and make an attempt to change lane.
Adaptive cruise control
A development of conventional cruise control that uses radar to maintain a set distance from the car in front. Should that car slow down, the system will automatically reduce the vehicle’s speed to match. If the car moves out of the way, it will accelerate back up to the pre-set cruising speed. Advanced versions even work in slow-moving traffic.
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 while others vibrate the seat or give visual warnings to alert the driver that it is time to take a break.
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 - linking the direction of the headlamp beam directly to the steering.
The most advanced systems not only allow the headlamps to turn as the wheels do, but 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) are designed to monitor your tyres, helping you maintain them at the correct pressures.
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 stable body shell
A stable 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.
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.
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.
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.
Historically, advances in car safety have focussed 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 in a collision, 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.
Isofix child seat mounts
Isofix is a system for fitting child seats that uses mounting points built into the car seats, rather than the adult 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, increasing the likelihood of it being installed correctly. Three-point Isofix systems are best, as they have a ‘top tether’ as well as two lower anchorages.
However, in crashes Isofix seats aren't automatically safer than belted seats. This is because the Isofix mounts create a stiff joint, through which crash forces are more readily transmitted to the seat shell and its occupant. With a belted seat, the compliance or 'give' in the belt allows some movement in a crash, absorbing some of the crash energy. Check out the unique Which? child car seat test results to find out which seats perform best of all in typical crashes.
We only award Best Buys to the safest child car seats. Find out which ones performed best.
Cars with a more ‘pedestrian-friendly’ front end should reduce the severity of injury to anyone unfortunate enough to be hit by a car – particularly at speeds of up to 30mph.
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.
For the lowdown on hundreds of new and used cars read our expert reviews.