Crash test standards: protecting people in cars

car crash investigationCredit: TRL

The speed and violence of crashes causes many deaths and injuries inside cars. Seat belts and child seats (properly fitted) are essential in preventing and mitigating levels of injury to vehicle occupants. They are a first line of defence. There are many other technologies that vehicle manufacturers can build into cars to protect occupants further (they do not replace the need for seatbelts). These technologies are known as "passive safety" measures. There is shockingly wide variance in passive safety measures in different cars on our roads and also variance in standards required by governments. 

Types of passive safety measures 

Passive safety measures include: 

  • Crumple zones (part of the exterior of the vehicle designed to deform in order to absorb the force of an impact, with the objective of leaving occupants protected in a hard shell);
  • Seat belt pre-tensioners (that automatically tighten a seat belt as a crash happens);
  • Seat belt pre- pre-tensioners (that can detect a crash is going to happen and tighten a seat belt in anticipation); 
  • Seat belt load limiter (prevents the seat belt load becoming too great; when a threshold force is reached the webbing is released in a controlled way from the reel, providing additional distance for the occupant to travel and change velocity within. It works with frontal airbags to manage the occupant’s energy during the impact);
  • Anchor systems bolted into the vehicle that child seats are fitted to;
  • Frontal air bags (that protect head and chest);
  • Side curtain air bags to the side of an occupant (deploys from the roof, and can protect an occupant’s head and chest, particularly in side impact collisions and rollovers);
  • Air bags in other positions, including knee airbags (which help prevent femur and pelvic fractures); airbags in the base of seats (that keep the occupant tightly within their seat belt); and seat belt air bags (that distribute forces over a wider area on your body and lowers the risk of more localised force causing fractures to bones or injury to internal organs);
  • Forgiving (softer) internal fittings (for example, dashboard made of softer plastics with underlying structures that are designed to distribute loading and avoid concentrated points which could produce high forces on impact).

Adaptive Restraint Systems 

Cars can also be fitted with Adaptive Restraint Systems (ARS), designed to adapt to circumstances of a crash (for example the speed) and nature of vehicle occupants (for example weight and height) and adjust accordingly restraint loads applied. This includes providing less forceful restraint in lower-speed crashes. These systems provide greater protection, particularly to people with more vulnerable bodies, notably older people who can suffer greater injury under given loading conditions because biomechanical tolerance to trauma reduces with age as bones weaken. ARS includes: 

  • Head restraints that move in a crash to provide extra protection against whiplash;
  • Steering columns that move in a crash (providing the driver with a bigger space in which to decelerate their movement forwards). 

The protection of older vehicle occupants is a cause for concern, partly because they sustain injuries more easily and severely than younger adults. [1]

Regulation of new vehicle standards

Governments have a major role to play in regulating the crashworthiness of new models of cars, requiring them to pass crash tests. The United Nations has stipulated minimum standards for protection of occupants in an off-set frontal crash test (hitting part of the front of the car) (regulation 94) and a lateral crash test (hitting the side of the car) (regulation 95). 

These two tests are carried out in controlled laboratory conditions, at defined speeds and must follow stipulated protocols. The tests involve Anthropometric Test Devices (ATDs), commonly referred to as crash test dummies, equipped to record dynamic behaviour and predict likely 'real world' injury. Different types of ATD are used for front and side impact tests and record parameters (deflection, force, velocity and deceleration) to assess and ensure a vehicle is within the regulated minimum performance standards based on the biomechanical risk of injury. To pass an impact test, dummies seat belted in the front seats only of the car must record injury ‘metrics’ below stipulated thresholds during the test.

The standard of the UN tests provide a minimum standard that all countries should sign up to. 

Tougher crash testing needed 

The standard of UN tests are important for governments everywhere to adopt. However, many crashes in the real world involve circumstances not covered by the parameters of the current UN tests. Tougher tests are necessary.

The frontal impact test only involves a collision with part of a car’s front. This is called an “offset” test and is designed to test the structural integrity of the car. Some real world collisions involve damage to the full width of the front. These full width collisions typically generate higher deceleration forces and test the seat belts and restraint systems much more than the offset test.

The side impact test simulates a car to car impact, but the striking car is replicated by a trolley, which has uniform stiffness and only weighs 950kg. The trolley is not representative of a modern car. A modern car on average weighs more than 1,200kg and has a complicated front structure that results in concentrated forces in varying places in the event of a collision. The side impact test conditions are also very different than those experienced in impacts with poles or trees, or with collisions with larger vehicles such as heavy goods vehicles, which strike higher, affecting upper body parts and heads of occupants.

There is no rear impact test. There is no testing involving dummies in rear seats.

Voluntary assessments by NCAP 

NCAP (new car assessment programme) is a plaudible voluntary crash testing programme, run by several different agencies in different regions of the world, that tests cars to higher standards than the UN tests and provides cars with star ratings for safety. Vehicle manufacturers voluntarily submit new models for testing and are awarded stars.

Different NCAPs conduct different tests, according to their available facilities. EuroNCAP, one of the most advanced NCAPs, includes, among other tests, a rear impact test for whiplash, a side impact test using a pole, and a full-width frontal impact test. ASEANCAP, based in Malaysia, carries out an offset frontal impact test but at a higher speed than that required in UN regulation 94. There is also an Australasian NCAP (ANCAP) and a Latin American NCAP (LatinNCAP). 

Global NCAP supports the development of New Car Assessment Programmes (NCAPs) in emerging markets where vehicle growth is strong but independent consumer information on crashworthiness is frequently not readily available and vehicles may be manufactured to variable standards despite having the same model name as vehicles sold in other countries. The charity highlights, very publically, vehicles that are shameful in their low levels of crashworthiness. 

Banning imports of unsafe cars   

Second-hand cars have been dumped on the poorest nations of the world, notably in Africa, with stories of large numbers of illegal imports into west Africa. Governments of nations affected by this problem have an important role to play in enforcing car imports and ensuring any cars entering their countries, among other rules, have:

  • met regulation 94 and 95 or equivalent;
  • also got seats, seat belts and head restraint systems that comply with the standards of UN regulations 14, 16 and 17.

References
[1] R Cuerden, M Edwards, M Seidl, for European Parliament's Committee on Regional Development, The impact of higher or lower weight and volume of cars on road safety, particularly for vulnerable users: analytical study, 2016