Choosing a safe and sustainable car

Features to protect you and others

Active control retractor

This is a type of seat belt retractor which works with other in-car systems to tighten the belt before a crash and then release it once the danger has passed. The active control retractor relies on information from other systems such as collision warning or ESC to tighten the belt before a crash actually happens, releasing it several seconds later if no crash occurs. See also safety belts under the basics and ITS under features to prevent a crash.

Adaptive restraints

These are in-car protection features that adapt to work differently depending on the size of the car’s occupants, or the type of accident. Although there is a great deal of research into this area, there are few features available yet for car buyers.

Air bags – front

Most air bags are frontal air bags. They work together with a safety belt to protect you in a front-on crash. The air bag is stored in the steering wheel hub or dashboard, and inflates in a split second after impact. As the force of a crash propels someone forward, the air bag protects them by ‘cushioning’ their body and slowing down the rate at which they’re moving.

You should always wear a safety belt whether or not the car you’re in has airbags.

Air bags are designed to supplement safety belts, not replace them. Some inflate only in crashes severe enough to threaten people wearing safety belts - and airbags aren’t as helpful as safety belts in some types of crashes, such as a rollover.

Dual stage front airbags inflate more or less depending on the size of the person in the car. Usually this size judgement is based on the position of the seat.

Air bags – side

Side impact airbags work in a side-on crash to protect people sitting on the struck side of the car. Side torso (chest protecting) airbags are usually in the seat by the door. Some of these also provide head protection.

‘Curtain’ airbags are located behind the roof trim above the doors, and cover the windows when they inflate. They usually cover front and rear windows, protecting people in both seats.

Head side airbags protect someone’s head from coming into contact with whatever object the car has hit – such as trees and poles. They can often prevent fatalities that would otherwise be inevitable in this type of crash.

Some facts about air bags

An air bag will not block the driver's vision in a crash - it inflates and deflates faster than you can blink.

Air bags are not soft. They must inflate incredibly quickly, which means the front of an air bag moves towards a person at between 160 to 320 km/h.

There is the potential for injury from air bags. To avoid this, newer air bags inflate more slowly. Some can adjust to different types of crash or passenger size.

Despite some risks, air bags do reduce injuries and have saved thousands of lives.

Air bags can’t be added to a car like some other equipment. They must be designed to work with the safety system of a specific model.

Some are bigger than others. Driver's air bags in European cars are usually about 30-45 litres; American models may be up to 70 litres. Passenger air bags are typically much bigger.

To avoid the risk of injury from an air bag:

• Always wear a safety belt.
• Don’t sit too close to the steering wheel or slide the seat a long way forward.
• Don’t rest anything over the air bag cover or put anything between you and the air bag (except a safety belt).
• Never put a rear-facing infant restraint in the front seat of a vehicle with a passenger air bag.
• If a car is in a crash and the airbag inflates, there is a legal requirement to replace the airbag if the car is less than 14 years old.
• Read your vehicle manual for any other information about its air bags.

Bonnet technology

Safety features in vehicle bonnets reduce the potential for injury to pedestrians. The gap between the underside of the bonnet and the top of the engine is maximised, ensuring the engine won’t strike a pedestrian’s head in an accident. There are also ‘deployable bonnets’ which sense an impact with a pedestrian and raise the bonnet to increase the gap between the bonnet and the engine.

Crumple zones and safety cages

In frontal, rear and offset crashes, modern vehicles protect occupants by absorbing crash energy and reducing the forces transmitted to the driver and passengers.

The front and rear of a vehicle act as crush zones designed to crumple in a controlled and progressive manner, allowing the occupant compartment to decelerate more slowly.

Slower deceleration means less force reaches the occupants, so there is a lower chance of injury.

Safety cages

The occupant compartment is a robust safety cage that diverts and dissipates crash energy and preserves the occupants' ‘survival space’ as much as possible.

The safety cage should include strong pillars to stop the roof from collapsing in roll-over crashes, as well as barriers to prevent the wheels, bonnet or engine intruding into the occupant compartment.

Door locks and hinges also form part of the safety cage and should remain intact so occupants are not thrown from the vehicle.

Door design

Some car doors have foam bolsters which crush and absorb impact in a crash. Door intrusion beams may be added as a cross brace below the window, though these may be better at preventing injuries when a car impacts with an object such as a tree or pole, than in crashes with another vehicle.

Frontal impact protection

Every car entering the New Zealand fleet must comply with one of the approved performance-based frontal impact protection standards. These standards ensure the front crumple zone, safety cage and other occupant protection features work together to provide a prescribed level of driver and passenger safety in a frontal crash.

• Standards for vehicles
• Lists of passenger cars that meet (or don't meet) New Zealand's frontal impact requirements

Frontal impact crash tests

The Australasian New Car Assessment Programme (ANCAP) provides information on the performance of vehicles in frontal impact crash tests that are even more rigorous than the tests done for standards compliance.

• ANCAP crash test results

Interiors – padding and edges

Most crash injuries happen when someone collides with something inside the car - such as the steering wheel or door. Improving the safety of the interior reduces the chance of serious injury. By law, newly registered cars must meet minimum standards for interior safety to reduce the chance of head injuries.

The dashboard, door panels, roof, sun visors, mirrors, header rail and pillars should have thick energy-absorbing padding with no sharp edges underneath.

Jutting objects and hard edges must be kept to a minimum. All interior fittings, controls and surfaces must comply with safety standards from the country of manufacture. As well as safety belts and airbags, there are other interior features that improve safety – such as collapsible steering columns and knee bolsters.

Knee bolsters

A knee bolster is a crushable barrier under the dashboard that stops a person’s knees from striking hard surfaces during a crash, reducing the likelihood of serious leg injuries for people sitting in the front seats. ‘Deployable’ knee bolsters are basically airbags for the knees.

Pretensioners

A feature built into some modern safety belt systems that removes the slack from the belt before a crash to better protect the person wearing it. For more, see safety belts under the basics.

Restraint control module (RCM)

A restraint control module is the computer that controls the release and timing of different protection features within a car, such as safety belt technology and airbags. When a crash is detected, the RCM triggers all these features in a certain order.

The RCM can also record the vehicle speed and deceleration of the crash, the firing times of the restraints systems and whether belts were worn. It could also provide signals to trigger emergency ITS systems to summon help.

Steering – collapsible column

In a crash, the driver is vulnerable to injuries from hitting the steering wheel or column. Collapsible columns are designed to ‘fold’ under impact to prevent injuries. This is a key way of keeping the driver safe, even in cars fitted with airbags.

Steering wheels, along with all other features inside a car, should be covered with thick energy-absorbing padding to minimise harm if they are hit by the driver in a crash.

Last updated: 16 July 2008