Whiplash is the most common injury in motor vehicle collisions, most often as a result of rear end or side impact collisions. Whiplash causes injury to the soft tissues of the bone and spinal cord in the neck and back, even in low-speed collisions. Whiplash injuries account for a large proportion of annual costs in terms of medical care and income support as well as lost productivity due to time away from work. Yet many drivers are unaware of the protective value of head restraints. Consequently, many drivers do not adjust their head restraints properly.
Current research suggests that serious neck injuries and associated disability can be reduced by 35% if the gap between research and policy and practice can be reduced (Farmer et al., 2008; Zuby & Lund, 2007). Vehicle safety researchers have shown that well designed head restraints, when used with safety seats, and seat belts, protect most passengers against sustaining any rear-end collision injuries. It has been shown that head restraints in rear-end collisions are as important as seat belts in frontal collisions.
Whiplash: The terms "whiplash" and "whiplash associated disorders" (WAD) are used to describe neck disorders related to sudden movement of the neck. Whiplash causes injury to the soft tissues of the bone and spinal cord in the neck and back; these injuries are often preventable.
Head Restraint: A device designed to limite the rearward displacement of an adult occupant;s head in relation to the torso in order to reduce the risk of injury to the cervical vertebrae in the event of a rear impact*.
Whiplash in Action
In order to understand what causes whiplash injuries, it is important to take a look at how the car seat and one's body interact during a rear-end collision. Below you can see in slow motion the way ones body moves when the vehicle gets hit from behind.
Phases of a rear-end motor vehicle collision:
- Rear car structure is impacted and begins to move forward and/or crushes
- Occupant remains stationary
- No occupant forces
- Car seat accelerates and pushes into occupant’s torso (i.e. central portion of the body in contact with seat)
- The torso loads the seat and is accelerated forward (seat will deflect rearward)
- Head remains stationary due to inertia
- Torso is accelerated by the car seat and may start to ramp up the seat
- Lower neck is pulled forward by the accelerated torso/seat
- The head rotates and extends rapidly rearward hyper-extending the neck
- Head is still moving backwards
- Car seat begins to spring forward
- The torso is again accelerated forward
- The head rotation is increased and is fully extended.
- Head and torso are accelerated forward ahead of the car seat
- Neck is “whipped” forward rotating and hyper-flexing the neck forward
The way the body moves in a rear-end collision is what influences the design of car seats and head restraints. Certain qualities are critical for a seat and head restraint system that protects vehicle occupants:
- Seat cushions minimizes occupant loading;
- Seat frame does not deflect significantly and does not fail;
- Safety restraint system is integrated into seat to retain occupant;
- Head restraint is properly designed and stiffness-matched with seat to reduce relative head/torso motion;
- Seat and head restraint are fully adjustable to accommodate all occupants (and easy to adjust to proper position).
Symptoms of whiplash include:
- Stiffness/neck pain
- Dizziness (nausea/vomitting)
- Problems thinking or remembering
- Numbness and tingling (arms, face, shoulders
- Jaw pain, lower back pain, hip pain
- Impaired vision
Research has shown there are numerous factors that contribute to whiplash-related injuries.
Individual-related risk factors:
- History of neck pain or injury
- Lower Body Mass Index (BMI)
- Tall drivers/occupants and head restraint geometry
Vehicle-related risk factors:
- Wearing a seatbelt
- Drivers and front-seated occupants
- Mass of the striking vehicle
- Speed of the striking vehicle
- Impact direction of the vehicle
- Extent of vehicle deformation
- Stiff vehicle structure
- Poor quality seats
Whiplash is Preventable
Researchers found the best way to prevent whiplash-related injuries is the correct adjustment and proper use of a head restraint. A properly adjusted head restraint help to protect against whiplash, and the potential for long-term injury, especially during rear collisions. The height of a restraint and the gap between the head and the restraint are critical in influencing injury risk. A correctly adjusted head restraint should be level with the top of the driver's ears or higher with minimal distance between the back of the head and the head rest.
Research indicates that during normal driving, if all adjustable head restraints were adjusted to the correct vertical height, then a reduction of 28.3% in whiplash injuries and a significant reduction in the incidence of soft tissue injuries, from rear-end collisions can be expected (Chapline et al., 2000; Viano & Gargan, 1995). More Statistics on Whiplash Injuries.
Properly Adjusted Head Restraints
To effectively reduce whiplash injury2:
- Raise the head restraint so the center is slightly above the top of the ear, and the top is level or above the top of the person’s head.
- Position the head restraint to be as close as possible to the back of the head.
- Adjust the seat back angle into a relatively upright position. This allows the head restraint to be positioned closer to the back of the head.
A poorly adjusted head restraint is set too low,too far from the back of the head or both of the above. This leaves the head and neck unsupported in the event of a rear-end collision.
A correctly positioned head restraint is set at the proper height for the individual paddenger and is about 5cm away from the back of the head. This will give the best protection for the head and neck in a rear-end collision.
Standards and Regulations
Vehicle manufacturers have been required to equip vehicles with head restraints since 1969 in the US, since 1972 in Australia and since 1978 in Canada and in Europe. The European regulations include a minimum height of 750 mm (29.5 in) and restraints must be adjustable to 800 mm (31.5 in) above the seating reference point. More standards and regulations
1. Statistic from the Insurance Corporation of British Columbia
2. Statistic from the Royal Society for Prevention of Accidents