Crash Mitigation and Collision Avoidance

Crash Mitigation and Collision Avoidance


This document has been compiled to highlight and summarise research regarding crash mitigation technologies which are commonly available. Crash mitigation is a field concerned with the hardware installed within vehicles or secured to the vehicle occupant, which can minimise injury in the event of a Road Traffic Incident (RTI). Typical crash mitigation technologies include:

  • Structural elements (Crumple zones and side impact protection);
  • Air Bags (including side and external airbags);
  • Head Restraints (including research on whiplash);
  • Underrun protection (involving the front, side and rear of Large Goods Vehicles);
  • Seat Belts (including pre-tensioners and smart seat belts); Child Restraints; and
  • Helmets (Motorcycle and Pedal Cycle).

The crash mitigation technologies of seat belts, child restraints and helmets are discussed in detail in dedicated research syntheses. Structural elements are briefly discussed to highlight their importance and how the relative performance vehicles are assessed. However, the main focus of this document will be research associated with airbags, head restraints and underrun protection.

Compared to seat belts, airbags are a relatively recent safety addition to vehicles. Frontal airbags are designed as part of a safety system acting together with the vehicles seat belt and seat to provide a means of absorbing the energy of a vehicles impact, resulting in protection for the driver and front seat passengers from the potential effects of occupants head and upper torso striking the steering wheel or dashboard. This design is most effective during a head-on RTI. More recent developments have included side airbags, which are intended to provide protection for the occupants from side-on RTIs, a scenario in which three-point seat belts have minimal mitigating effects.

Airbags have also been designed to deploy from the outside of the vehicle in order to reduce injuries to motorcyclists and pedal cyclists. However, concerns have been raised regarding their limited usefulness and potential to inflict further injury. Conversely, research concerning airbags for pedestrians has been more positive and vehicle manufacturers are beginning to install this technology.

Head restraints are an undervalued crash mitigation technology, and have the potential to effect large-scale road safety improvements. Head restraints, when correctly positioned, can reduce the likelihood of whiplash to occupants of vehicles which are struck during a rear striking RTI. Whilst there is a legal requirement for vehicles to have head restraints fitted in the UK, there are problems with occupants having them configured at an incorrect height; consequently they have minimal effect in mitigating whiplash.

The final crash mitigation technology discussed in this synthesis is underrun protection. Underrun occurs when a Large Goods Vehicle (LGV) or other large vehicle turns and causes smaller vehicles or pedestrians to become trapped between the axles and wheels of that vehicle. Side underrun protection consists of filling the space between the axles of a large vehicle so that smaller road vehicles cannot accidentally enter the area. Front and rear underrun protection involves a similar approach in that the area beneath the front and rear lights of a large vehicle is filled to create a solid environment that is akin to a smaller vehicle striking an immovable object (such as a wall). Whilst this might sound dangerous, it is less likely to cause injury, especially to occupants of smaller vehicles.


  • Date Added: 03 Apr 2012, 08:18 AM
  • Last Update: 30 Jan 2017, 02:38 PM