Passive safety

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Car safety is the avoidance of car accidents or the minimization of harmful effects of accidents, in particular as pertaining to human life and health. Special safety features have been built into cars for years, some for the safety of car's occupants only, some for the safety of others.

Distance crossed by vehicles in a city (here, Paris) during 1 second (typical time to react to an emergency).

Road traffic injuries represent about 25% of worldwide injury-related deaths (the leading cause) with an estimated 1.26 million deaths in 2000 (Peden 2002).

Major factors in accidents include driving under the influence of alcohol or other drugs; inattentive driving; driving while fatigued or unconscious; encounters with road hazards such as snow, potholes, and crossing animals; or reckless driving.


Car safety became an issue almost immediately after the invention of the automobile, when Nicolas-Joseph Cugnot crashed his steam-powered "Fardier" against a wall in 1771. One of the earliest recorded automobile fatalities was Mary Ward, on August 31, 1869 in Parsonstown, Ireland.

In 1958, the United Nations established the World Forum for Harmonization of Vehicle Regulations, an international standards body advancing auto safety. Many of the most life saving safety innovations, like seat belts and roll cage construction were brought to market under its auspices.

In 1966, the US established the United States Department of Transportation (DOT) with automobile safety one of its purposes. The National Transportation Safety Board (NTSB) was created as an independent organization on April 1, 1967, but was reliant on the DOT for administration and funding. However, in 1975 the organization was made completely independent by the Independent Safety Board Act.

The NTSB and its European equivalent, EuroNCAP have each issued independent safety tests for all new automobiles, without reciprocity.

In June, 2004 the NTSB released new tests designed to test the rollover risk of new cars and SUVs. Only the Mazda RX-8 got a 5-star rating. However, the correlation between official crash test results and road deaths in vehicles is not exact. An alternative method of assessing vehicle safety is to study the road accident statistics on a model-by-model basis.

Despite technological advances, the death toll of car accidents remains high: about 40,000 people die every year in the US. While this number increases annually in line with rising population and increased travel, the rate per capita and per vehicle miles travelled decreases. In 1996 the US has about 2 deaths per 10,000 motor vehicles, comparable to 1.9 in Germany, 2.6 in France, and 1.5 in the UK [1]. In 1998 there were 3,421 fatal accidents in the UK, the fewest since 1926 [2].

A much higher number of accidents result in permanent disability.


A Swedish study found pink cars safest, with black cars most likely to be involved in crashes, and also showed Saab to be the "safest car in Sweden [In terms of passive safety]" (Land transport NZ 2005).

An Auckland, New Zealand study found a significantly lower risk of serious injury in silver cars; with high risks for brown, black, and green cars. (Furness et al, 2003).

Pregnant women

When pregnant, women should continue to use seatbelts and airbags properly. A University of Michigan study found that "unrestrained or improperly restrained pregnant women are 5.7 times more likely to have an adverse fetal outcome than properly restrained pregnant women" [3]. If seatbelts are not long enough, extensions are available from the car manufacturer or an aftermarket supplier.


Car safety is especially critical for young children, as car safety is generally designed for normal sized adults. Safety features that could save an adult can actually cause more damage to a child than if the feature was not there. It is important to review with others, who may be supervising the child, the rules for car safety. All children age 12 and under should ride in the back seat. This is especially the case if there are airbags in the front seat, as airbags are only designed to protect adults and may injure children.

Child safety locks prevent children from accidentally opening doors from inside the vehicle, even if the door is unlocked. The door, once unlocked, can then be opened only from the outside.


Newborn babies should be put in a car seat until they weigh at least 20 or 22 pounds (10 or 11 kg). These carriers are designed to be placed in the rear seat and face towards the rear with the baby looking towards the back window. Some of these carriers are "Convertibles" which can also be used forward facing for older children. With infants, these should only be used facing the rear. Harness straps should be at or below shoulder level.

A rear-facing infant restraint must never be put in the front seat of a vehicle with a front passenger air bag. A rear-facing infant restraint places an infant's head close to the air bag module, which can cause severe head injuries or death if the air bag deploys. Modern cars include a switch to turn off the airbag system of the passenger seat, in which case a child-supporting seat must be installed.


Toddlers over 1 year old and between 20 and 40 pounds (10 and 20 kg) should be placed in forward facing child seats or convertibles placed in the rear seat. Harness straps should be at or above the child's shoulders.

Young children

Children who weigh less than 80 pounds (40 kg), are younger than 8, or are shorter than 4 ft 9 in (1.4 m) are advised to use belt positioning booster seats which raise them to a level that allows seat belts to work effectively. These seats are forward facing and must be used with both lap and shoulder belts.

Make sure the lap belt fits low and tight across the lap/upper thigh area and the shoulder belt fits snug crossing the chest and shoulder to avoid abdominal injuries.

There are two main types of booster seats. If the car's back seat is lower than the child's ears, a high back booster seat should be used to help protect the child's head and neck. If the car's seat back is higher than the child's ears, a backless booster seat can be used.

Teenage Drivers

Most areas in the United States allow teens the privilege to drive at the age of 16. This age ranges in other countries but all teen drivers are relatively inexperienced compared to other drivers. This lack of experience leads to an increased risk of accidents among this demographic. Several resources are available to help teen drivers including TeenDriving.comand's kids first car tips and recommendations.

Safety features


To make driving safer and prevent accidents from occurring, cars may have the following active safety features:

Damage control

Front drivers-side airbag

When an accident is imminent, various passive safety systems work together to minimize damage to those involved. Much research has been done using crash test dummies to make modern cars safer than ever. Recently, attention has also been given to cars' design regarding the safety of pedestrians in car-pedestrian collisions. Controversial proposals in Europe would require cars sold there to have a minimum/maximum hood height. This has caused automakers to complain that the requirements will restrict their design choices, resulting in ugly cars. Others have pointed out that a notable percentage of pedestrians in these accidents are drunk. From 2006 the use of "bull bars" (known as "roo bars" in Australia), in fashion on 4x4s and SUVs, will be illegal.

  • Seatbelts (or safety belts) keep a person from being thrown forward or ejected from the vehicle.
  • Airbags
    • Front airbags inflate in a medium speed head on collisions to cushion the blow of a head on the dashboard or steering wheel.
    • Side airbags inflate in a side (T-bone) collision to cushion the torso
    • Curtain airbags protect the heads of passengers in a side collision
  • Bumpers to withstand low-speed collisions without damaging bodywork.
  • Crumple zones absorb the energy of an impact when the car hits something
    • Crash box to dissipate impact forces
  • Collapsible steering column, sometimes provided with steel sheet bellows.
  • Crash compatibility can be improved by matching vehicles by weight and by matching crumple zones with points of structural rigidity, particularly for side-on collisions. Some pairs of vehicle front end structures interact better than others in crashes. Widely different height and body on rail frame design are particularly bad.
  • Cage construction is designed to protect vehicle occupants. Some racing vehicles have a tubular roll cage
  • Reinforced side door structural members
  • Fuel pump shutoff devices turn off gas flow in the event of a collision for the purpose of preventing gasoline fires.
  • Light weight: the possible damage a vehicle can do to outside people and things is roughly proportional to its kinetic energy, which is its weight times the square of its speed.
  • Active pedestrian protection systems [4].

See also

External links


  • IEEE Communications Magazine, April 2005, "Ad Hoc Peer-to-Peer Network Architecture for Vehicle Safety Communications"
  • IEEE Communications Magazine, April 2005, "The Application-Based Clustering Concept and Requirements for Intervehicle Networks"
  • Physics Today, January 2006, "Vehicle Design and the Physics of Traffic Safety"