Other sections in this guide
- Overview
- Car safety features explained
- Primary safety explained
- Secondary safety explained
- Top five tips for buying a safe car
Car safety and child seats Secondary safety explained
Secondary safety features
Since Which? began campaigning to improve car safety, manufacturers have really started competing to make their cars the safest by coming up with innovative new designs and selling 'safety' as a benefit of buying their car. Here, we explain what 'secondary' safety features are and highlight the main ones available.
1. A stable body shell
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A stable car body shell resists 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 detail of the ratings and not just the headline star rating.
2. Pre-tensioned and load-limited seatbelts
Seatbelt pre-tensioners take up any slack in the belt when they detect a crash is imminent. 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 load is placed on the seat’s occupant.
Airbags - a great safety feature
3. 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 its deceleration and in-crash circumstances, then trigger the firing of 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.
4. 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 a 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. The front seats are tested in Euro NCAP testing to check their resistance to whiplash injury.
5. 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 when the seat is moved.
6. 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.
7. Knee airbags
Historically, car designers gave little thought to how the car's interior could harm the occupants when it deformed in a crash. But as awareness grew, not only did they attempt to control the way the car collapsed, they also began thinking about the interior components that might cause crippling injuries to the front seat occupants.
The presence of the steering column, often with a knee-level steering column lock and ignition key meant that if the crash caused these to be pushed back the driver could really suffer. Many makers moved away from mounting the column lock in this position, but even so, the column itself remained.
Then forward-thinking designers like Toyota and Ford decided a well-positioned airbag (inside the shroud surrounding the column, or behind the main facia trim), could prevent the sorts of knee and pelvis injury seen in older designs.
8. 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. The Britax Duo Plus was among the first Isofix seats on the market, but many makers have followed since. 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 hence the child. With a belted seat, the compliance or 'give' in the belt allows some movement in a crash, absorbing some of the crash energy. As long as you follow the instructions, Isofix should make fitting a child car seat easier, but check out the unique Which? child car seat test results to find out which seats perform best of all in typical crashes.
9. Pedestrian protection
Pedestrian protection is given more importance
Cars with a more ‘pedestrian-friendly’ front end should reduce the severity of injury if you’re unfortunate enough to hit a pedestrian – particularly at speeds of up to 30mph.
The key to this is twofold. Firstly, the manufacturer should be considering making the bonnet and surrounding body panels as compliant as possible (to absorb impact energy). Secondly, they should be trying to avoid pedestrian contact with any harder components, either on the exterior of the car (eg wiper mounting points or linkage), or hidden beneath the compliant panels. The approach to this is to hide all the wiper components away from the impact area, and to allow a suitably large packaging envelope around all the hard under-bonnet components, like the engine.
Some manufacturers offer an alternative to this with the pop-up bonnet. When the car senses there is about to be a pedestrian impact, the bonnet is pushed upwards, creating additional space between it and the hard, potentially injury-causing under-bonnet components. This also creates an energy-absorbing cushioning affect as the falling pedestrian lands on the bonnet and pushes against the springs. Look for cars with a high Euro NCAP pedestrian safety score.
