Seatbelt
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A seat belt (also known as a safety belt, or spelled seatbelt) is a vehicle safety device designed to secure the driver or a passenger of a
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), ...
against harmful movement that may result during a collision or a sudden stop. A seat belt reduces the likelihood of death or serious
injury An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, o ...
in a traffic collision by reducing the force of secondary impacts with interior strike hazards, by keeping occupants positioned correctly for maximum effectiveness of the
airbag An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. T ...
(if equipped), and by preventing occupants being ejected from the vehicle in a crash or if the vehicle rolls over. When in motion, the driver and passengers are traveling at the same speed as the vehicle. If the vehicle suddenly stops or crashes, the occupants continue at the same speed the vehicle was going before it stopped. A seatbelt applies an opposing force to the driver and passengers to prevent them from falling out or making contact with the interior of the car (especially preventing contact with, or going through, the
windshield The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. ...
). Seatbelts are considered primary restraint systems (PRSs), because of their vital role in occupant safety.


Effectiveness

An analysis conducted in the United States in 1984 compared a variety of seat belt types alone and in combination with air bags. The range of fatality reduction for front seat passengers was broad, from 20% to 55%, as was the range of major injury, from 25% to 60%. More recently, the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...
has summarized these data by stating "seat belts reduce serious crash-related injuries and deaths by about half." Most seatbelt malfunctions are a result of there being too much slack in the seatbelt at the time of the accident. It has been suggested that although seat belt usage reduces the probability of death in any given accident, mandatory seat belt laws have little or no effect on the overall number of traffic fatalities because seat belt usage also disincentivizes safe driving behaviors, thereby increasing the total number of accidents. This idea, known as compensating-behavior theory, is not supported by the evidence. In case of
vehicle rollover A rollover is a type of vehicle crash in which a vehicle tips over onto its side or roof. Rollovers have a higher fatality rate than other types of vehicle collisions. Dynamics Vehicle rollovers are divided into two categories: tripped and un ...
in a US passenger car or SUV, from 1994 to 2004, wearing seat belt reduced the risk of fatalities or incapacitating injuries and increased the probability of no injury: * In case of
vehicle rollover A rollover is a type of vehicle crash in which a vehicle tips over onto its side or roof. Rollovers have a higher fatality rate than other types of vehicle collisions. Dynamics Vehicle rollovers are divided into two categories: tripped and un ...
in a US passenger car, there are % fatalities in 1994 and % in 2014 when user is restrained.DOT HS 810 741 4. Title and Subtitle 5. Report Date An Analysis of Motor Vehicle Rollover Crashes and March 2007 Injury outcomes There are % fatalities in 1994 and % in 2014 when user is unrestrained. * In case of vehicle rollover, there are % incapacitating injury in 1994 and % in 2014 when user is restrained. There are % incapacitating injury in 1994 and % in 2014 when user is unrestrained. * The probability of no injury is % in 1994 and % in 2014 when user is restrained. There are % no injury in 1994 and % in 2014 when user is unrestrained.


History

Seatbelts were invented by English engineer
George Cayley Sir George Cayley, 6th Baronet (27 December 1773 – 15 December 1857) was an English engineer, inventor, and aviator. He is one of the most important people in the history of aeronautics. Many consider him to be the first true scientific aeri ...
, to use on his glider, in the mid-19th century. In 1946, C. Hunter Shelden opened a neurological practice at
Huntington Memorial Hospital Huntington may refer to: Places Canada * Huntington, Nova Scotia New Zealand * Huntington, New Zealand a suburb in Hamilton, New Zealand United Kingdom * Huntington, Cheshire, England * Huntington, East Lothian, Scotland * Huntington, ...
in
Pasadena, California Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. I ...
. In the early 1950s, Shelden made a major contribution to the automotive industry with his idea of retractable seat belts. This came about from his care of the high number of head injuries coming through the emergency room. He investigated the early seat belts with primitive designs that were implicated in these injuries and deaths. Nash was the first American car manufacturer to offer seat belts as a factory option, in its 1949 models. They were installed in 40,000 cars, but buyers did not want them and requested dealers to remove them. The feature was "met with insurmountable sales resistance" and Nash reported that after one year "only 1,000 had been used" by customers. Ford offered seat belts as an option in 1955. These were not popular, with only 2% of Ford buyers choosing to pay for seatbelts in 1956. To reduce the high level of injuries Shelden was seeing, he proposed, in late 1955, retractable seat belts, recessed
steering wheel A steering wheel (also called a driving wheel (UK), a hand wheel, or simply wheel) is a type of steering control in vehicles. Steering wheels are used in most modern land vehicles, including all mass-production automobiles, buses, light and ...
s, reinforced roofs, roll bars, automatic door locks, and passive restraints such as
air bag An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a Traffic collision, collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and a ...
s. Subsequently, in 1966, Congress passed the National Traffic and Motor Vehicle Safety Act, requiring all automobiles to comply with certain safety standards. Glenn W. Sheren, of
Mason, Michigan Mason is the county seat of Ingham County, Michigan, Ingham County in the U.S. state of Michigan. The population was 8,252 at the 2010 United States Census, 2010 census. Mason is the only city in the United States that serves as a county seat a ...
, submitted a patent application on March 31, 1955, for an automotive seat belt and was awarded in 1958. This was a continuation of an earlier patent application that Sheren had filed on September 22, 1952. However, the first modern three-point seat belt (the so-called ''CIR-Griswold restraint'') commonly used in consumer vehicles was patented in 1955 by the Americans Roger W. Griswold and
Hugh DeHaven Hugh DeHaven (3 March 1895 – 13 February 1980) was an American pilot, engineer and passive safety pioneer. DeHaven survived a plane crash while training as a Royal Canadian Flying Corps pilot during the First World War, and became interested in ...
.
Saab Saab or SAAB may refer to: Brands and enterprises * Saab Group, a Swedish aerospace and defence company, formerly known as SAAB, and later as Saab AB ** Datasaab, a former computer company, started as spin off from Saab AB * Saab Automobile, a fo ...
introduced seat belts as standard equipment in 1958. After the Saab GT 750 was introduced at the New York Motor Show in 1958 with safety belts fitted as standard, the practice became commonplace.
Vattenfall Vattenfall is a Swedish multinational power company owned by the Swedish State. Beyond Sweden, the company generates power in Denmark, Finland, Germany, the Netherlands, and the United Kingdom. The company's name is Swedish for "waterfall", and ...
, the Swedish national electric utility, did a study of all fatal, on-the-job accidents among their employees. The study revealed that the majority of fatalities occurred while the employees were on the road on company business. In response, two Vattenfall safety engineers, Bengt Odelgard and Per-Olof Weman, started to develop a seat belt. Their work was presented to Swedish manufacturer
Volvo The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...
in the late 1950s, and set the standard for seat belts in Swedish cars. The three-point seatbelt was developed to its modern form by Swedish inventor
Nils Bohlin Nils Ivar Bohlin (17 July 1920 – 21 September 2002) was a Swedish mechanical engineer and inventor who invented the three-point safety belt while working at Volvo. Biography Born in Härnösand, Sweden, Bohlin received a diploma in mechan ...
for Volvo—who introduced it in 1959 as standard equipment. In addition to designing an effective three-point belt, Bohlin demonstrated its effectiveness in a study of 28,000 accidents in Sweden. Unbelted occupants sustained fatal injuries throughout the whole speed scale, whereas none of the belted occupants were fatally injured at accident speeds below 60 mph. No belted occupant was fatally injured if the passenger compartment remained intact. Bohlin was granted for the device. The first compulsory
seat belt law Seat belt legislation requires the fitting of seat belts to motor vehicles and the wearing of seat belts by motor vehicle occupants to be mandatory. Laws requiring the fitting of seat belts to cars have in some cases been followed by laws mandati ...
was put in place in 1970, in the state of
Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...
,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, requiring their use by drivers and front-seat passengers. This legislation was enacted after trialing Hemco seatbelts, designed by Desmond Hemphill (1926–2001), in the front seats of police vehicles, lowering the incidence of officer injury and death. Mandatory
seatbelt laws in the United States A seat belt (also known as a safety belt, or spelled seatbelt) is a vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt reduc ...
began to be introduced in the 1980s and faced opposition, with some consumers going to court to challenge the laws. Some cut seatbelts out of their cars.


Types


Two-point

A two-point belt attaches at its two endpoints. A simple strap was first used March 12, 1910, by pilot
Benjamin Foulois Benjamin Delahauf Foulois (December 9, 1879 – April 25, 1967) was a United States Army general who learned to fly the first military planes purchased from the Wright brothers. He became the first military aviator as an airship pilot, and achi ...
, a pioneering aviator with the
Aeronautical Division, U.S. Signal Corps The Aeronautical Division, Signal Corps, Appendix 2 (1907–1914) was the first heavier-than-air military aviation organization in history and the progenitor of the United States Air Force. A component of the U.S. Army Signal Corps, the Aeronaut ...
, so he might remain at the controls during turbulence. The Irvin Air Chute Company made the seat belt for use by professional race car driver
Barney Oldfield Berna Eli "Barney" Oldfield (January 29, 1878 – October 4, 1946) was an American pioneer automobile racer; his "name was synonymous with speed in the first two decades of the 20th century". After success in bicycle racing, he began auto r ...
when his team decided the daredevil should have a "safety harness" for the 1923
Indianapolis 500 The Indianapolis 500, formally known as the Indianapolis 500-Mile Race, and commonly called the Indy 500, is an annual automobile race held at Indianapolis Motor Speedway (IMS) in Speedway, Indiana, United States, an enclave suburb of Indi ...
.


Lap

A lap belt is a strap that goes over the waist. This was the most common type of belt prior to legislation requiring three-point belts and is found in older cars.
Coaches Coach may refer to: Guidance/instruction * Coach (sport), a director of athletes' training and activities * Coaching, the practice of guiding an individual through a process ** Acting coach, a teacher who trains performers Transportation * Coac ...
are equipped with lap belts (although many newer coaches have three-point belts), as are passenger aircraft seats. University of Minnesota professor James J. (Crash) Ryan was the inventor of, and held the patent for, the automatic retractable lap safety belt.
Ralph Nader Ralph Nader (; born February 27, 1934) is an American political activist, author, lecturer, and attorney noted for his involvement in consumer protection, environmentalism, and government reform causes. The son of Lebanese immigrants to the Un ...
cited Ryan's work in ''
Unsafe at Any Speed ''Unsafe at Any Speed: The Designed-In Dangers of the American Automobile'' is a non-fiction book by consumer advocate Ralph Nader, first published in 1965. Its central theme is that car manufacturers resisted the introduction of safety features ( ...
'' and, in 1966, President
Lyndon Johnson Lyndon Baines Johnson (; August 27, 1908January 22, 1973), often referred to by his initials LBJ, was an American politician who served as the 36th president of the United States from 1963 to 1969. He had previously served as the 37th vice ...
signed two bills requiring safety belts in all passenger vehicles starting in 1968. Until the 1980s, three-point belts were commonly available only in the front outboard seats of cars; the back seats were often only fitted with lap belts. Evidence of the potential of lap belts to cause separation of the
lumbar vertebrae The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse p ...
and the sometimes-associated
paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
, or "
seat belt syndrome Seat belt syndrome is a collective term that includes all injury profiles associated with the use of seat belts. It is defined classically as a ''seat belt sign'' (seat belt marks on the body) plus an intra-abdominal organ injury (e.g. bowel perfor ...
" led to the progressive revision of passenger safety regulations in nearly all developed countries to require three-point belts, first in all outboard seating positions, and eventually in all seating positions in passenger vehicles. Since September 1, 2007, all new cars sold in the US require a lap and shoulder belt in the center rear seat. In addition to regulatory changes, "seat belt syndrome" has led to a liability for vehicle manufacturers. One Los Angeles case resulted in a $45 million jury verdict against Ford; the resulting $30 million judgment (after deductions for another defendant who settled prior to trial) was affirmed on appeal in 2006.


Sash

A "sash" or shoulder harness is a strap that goes diagonally over the vehicle occupant's outboard shoulder and is buckled inboard of his or her lap. The shoulder harness may attach to the lap belt tongue, or it may have a tongue and buckle completely separate from those of the lap belt. Shoulder harnesses of this separate or semi-separate type were installed in conjunction with lap belts in the outboard front seating positions of many vehicles in the North American market starting at the inception of the shoulder belt requirement of the US
National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...
's (NHTSA) Federal Motor Vehicle Safety Standard 208 on January 1, 1968. However, if the shoulder strap is used without the lap belt, the vehicle occupant is likely to "submarine", or slide forward in the seat and out from under the belt, in a frontal collision. In the mid-1970s, three-point belt systems such as Chrysler's "Uni-Belt" began to supplant the separate lap and shoulder belts in American-made cars, though such three-point belts had already been supplied in European vehicles such as Volvo,
Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
, and Saab for some years.


Three-point

A three-point belt is a Y-shaped arrangement, similar to the separate lap and sash belts, but unified. Like the separate lap-and-sash belt, in a collision, the three-point belt spreads out the energy of the moving body over the chest, pelvis, and shoulders. Volvo introduced the first production three-point belt in 1959. The first car with a three-point belt was a Volvo PV 544 that was delivered to a dealer in
Kristianstad Kristianstad (, ; older spelling from Danish language, Danish ''Christianstad'') is a Urban areas in Sweden, city and the seat of Kristianstad Municipality, Scania County, Sweden with 40,145 inhabitants in 2016. During the last 15 years, it has ...
on August 13, 1959. However, the first car model to have the three-point seat belt as a standard item was the 1959
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, first outfitted with a two-point belt at initial delivery in 1958, replaced with the three-point seat belt the following year. The three-point belt was developed by
Nils Bohlin Nils Ivar Bohlin (17 July 1920 – 21 September 2002) was a Swedish mechanical engineer and inventor who invented the three-point safety belt while working at Volvo. Biography Born in Härnösand, Sweden, Bohlin received a diploma in mechan ...
who had earlier also worked on
ejection seat In aircraft, an ejection seat or ejector seat is a system designed to rescue the aircraft pilot, pilot or other aircrew, crew of an aircraft (usually military) in an emergency. In most designs, the seat is propelled out of the aircraft by an ex ...
s at
Saab Saab or SAAB may refer to: Brands and enterprises * Saab Group, a Swedish aerospace and defence company, formerly known as SAAB, and later as Saab AB ** Datasaab, a former computer company, started as spin off from Saab AB * Saab Automobile, a fo ...
. Volvo then made the new seat belt design patent open in the interest of safety and made it available to other car manufacturers for free.


Belt-in-Seat

The Belt-in-Seat (BIS) is a three-point harness with the shoulder belt attached to the seat itself, rather than to the vehicle structure. The first car using this system was the
Range Rover Classic The Range Rover Classic is a 4x4, mid-size Sport utility vehicle series produced from 1969 to 1996 – initially by the Rover (later Land Rover) division of British Leyland, and latterly by the Rover Group. The first generation of vehicles produ ...
, which offered BIS as standard on the front seats from 1970. Some cars like the
Renault Vel Satis The Renault Vel Satis is an executive car that was produced by the French manufacturer Renault, launched at the 2001 Geneva Motor Show to replace the already discontinued Safrane. It was previously revealed as a concept car in 1998, at the Paris ...
use this system for the front seats. A
General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
assessment concluded seat-mounted three-point belts offer better protection especially to smaller vehicle occupants, though GM did not find a safety performance improvement in vehicles with seat-mounted belts versus belts mounted to the vehicle body. Belt-in-Seat type belts have been used by automakers in convertibles and pillarless hardtops, where there is no "B" pillar to affix the upper mount of the belt. Chrysler and Cadillac are well known for using this design. Antique auto enthusiasts sometimes replace original seats in their cars with BIS-equipped front seats, providing a measure of safety not available when these cars were new. However, modern BIS systems typically use electronics that must be installed and connected with the seats and the vehicle's electrical system in order to function properly.


4-, 5-, and 6-point

Five-point harnesses are typically found in child safety seats and in
racing In sport, racing is a competition of speed, in which competitors try to complete a given task in the shortest amount of time. Typically this involves traversing some distance, but it can be any other task involving speed to reach a specific goa ...
cars. The lap portion is connected to a belt between the
leg A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element ca ...
s and there are two shoulder belts, making a total of five points of attachment to the seat. A 4-point harness is similar, but without the strap between the legs, while a 6-point harness has two belts between the legs. In
NASCAR The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
, the 6-point harness became popular after the
death of Dale Earnhardt On the afternoon of February 18, 2001, American stock car racing driver and team owner Dale Earnhardt was killed instantly due to a basilar skull fracture in a final-lap collision in the 2001 Daytona 500, in which he crashed into a retaining wa ...
, who was wearing a five-point harness when he suffered his fatal crash; as it was first thought that his belt had broken, and broke his neck at impact, some teams ordered a six-point harness in response.


Seven-point

Aerobatic Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glid ...
aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
frequently uses a combination harness consisting of a five-point harness with a redundant lap-belt attached to a different part of the aircraft. While providing redundancy for negative-g maneuvers (which lift the pilot out of the seat), they also require the pilot to un-latch two harnesses if it is necessary to parachute from a failed aircraft.


Seatbelt airbag

Seatbelt
airbag An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. T ...
s are available in some models of Ford and Mercedes.


Technology


Locking retractors

The purpose of locking retractors is to provide the seated occupant the convenience of some free movement of the upper torso within the compartment while providing a method of limiting this movement in the event of a crash. Starting in 1996, all passenger vehicle seatbelts must lock pre-crash meaning they have a locking mechanism in the retractor or in the latch plate. Seat belts are stowed on spring-loaded reels called "retractors" equipped with
inertia Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
l locking mechanisms that stop the belt from extending off the reel during severe deceleration. There are two main types of inertial seat belt locks. A webbing-sensitive lock is based on a
centrifugal clutch A centrifugal clutch is an automatic clutch that uses centrifugal force to operate. The output shaft is disengaged at low rotational speed and engages more as speed increases. It is often used in mopeds, underbones, lawn mowers, go-karts, chainsaw ...
activated by the rapid acceleration of the strap (webbing) from the reel. The belt can be pulled from the reel only slowly and gradually, as when the occupant extends the belt to fasten it. A sudden rapid pull of the belt—as in a sudden braking or collision event—causes the reel to lock, restraining the occupant in position. The first automatic locking retractor for seat belts and shoulder harnesses in the U.S. was the Irving "Dynalock" safety device. These "Auto-lock" front lap belts were optional on AMC cars with bucket seats in 1967. A vehicle-sensitive lock is based on a
pendulum A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the ...
swung away from its plumb position by rapid deceleration or rollover of the vehicle. In the absence of rapid deceleration or rollover, the reel is unlocked and the belt strap may be pulled from the reel against the spring tension of the reel. The vehicle occupant can move around with relative freedom while the spring tension of the reel keeps the belt taut against the occupant. When the pendulum swings away from its normal plumb position due to sudden deceleration or rollover, a pawl is engaged, the reel locks and the strap restrains the belted occupant in position. Dual-sensing locking retractors use both vehicle G-loading and webbing payout rate to initiate the locking mechanism.


Pretensioners and webclamps

Seatbelts in many newer vehicles are also equipped with "pretensioners" or "web clamps", or both. Pretensioners preemptively tighten the belt to prevent the occupant from jerking forward in a crash. Mercedes-Benz first introduced pretensioners on the 1981 S-Class. In the event of a crash, a pretensioner will tighten the belt almost instantaneously. This reduces the motion of the occupant in a violent crash. Like airbags, pretensioners are triggered by sensors in the car's body, and many pretensioners have used explosively expanding gas to drive a piston that retracts the belt. Pretensioners also lower the risk of "submarining", which occurs when a passenger slides forward under a loosely fitted seat belt. Some systems also pre-emptively tighten the belt during fast accelerations and strong decelerations, even if no crash has happened. This has the advantage that it may help prevent the driver from sliding out of position during violent evasive maneuvers, which could cause loss of control of the vehicle. These pre-emptive safety systems may ''prevent'' some collisions from happening, as well as reduce injuries in the event an actual collision occurs. Pre-emptive systems generally use electric pretensioners which can operate repeatedly and for a sustained period, rather than pyrotechnic pretensioners, which can only operate a single time. Webclamps stop the webbing in the event of an accident and limit the distance the webbing can spool out (caused by the unused webbing tightening on the central drum of the mechanism). These belts also often incorporate an energy management loop ("rip stitching") in which a section of the webbing is looped and stitched with special stitching. The function of this is to "rip" at a predetermined load, which reduces the maximum force transmitted through the belt to the occupant during a violent collision, reducing injuries to the occupant. A study demonstrated that standard automotive three-point restraints fitted with pyrotechnic or electric pretensioners were not able to eliminate all interior passenger compartment head strikes in rollover test conditions. Electric pretensioners are often incorporated on vehicles equipped with
precrash system A collision avoidance system (CAS), also known as a pre-crash system, forward collision warning system, or collision mitigation system, is an advanced driver-assistance system designed to prevent or reduce the severity of a collision. In its ...
s; they are designed to reduce seat belt slack in a potential collision and assist in placing the occupants in a more optimal seating position. The electric pretensioners also can operate on a repeated or sustained basis, providing better protection in the event of an extended rollover or a multiple collision accident.


Inflatable

The inflatable seatbelt was invented by Donald Lewis and tested at the Automotive Products Division of
Allied Chemical Corporation Allied Corp. was a major American company with operations in the chemical, aerospace, automotive, oil and gas industries. It was initially formed in 1920 as the Allied Chemical and Dye Corporation as an amalgamation of five chemical companies. In ...
. Inflatable seatbelts have tubular inflatable bladders contained within an outer cover. When a crash occurs the bladder inflates with gas to increase the area of the restraint contacting the occupant and also shortening the length of the restraint to tighten the belt around the occupant, improving the protection. The inflatable sections may be shoulder-only or lap and shoulder. The system supports the head during the crash better than a web-only belt. It also provides side impact protection. In 2013, Ford began offering rear-seat inflatable seat belts on a limited set of models, such as the
Explorer Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...
and
Flex Flex or FLEX may refer to: Computing * Flex (language), developed by Alan Kay * FLEX (operating system), a single-tasking operating system for the Motorola 6800 * FlexOS, an operating system developed by Digital Research * FLEX (protocol), a comm ...
.


Automatic

Seatbelts that automatically move into position around a vehicle occupant once the adjacent door is closed and/or the engine is started were developed as a countermeasure against low usage rates of manual seat belts, particularly in the United States. The 1972
Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German Automotive industry, motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a ...
ESVW1
Experimental Safety Vehicle Experimental Safety Vehicle (ESV) is the designation for experimental concept cars which are used to test car safety ideas. In 1973, the United States Department of Transportation, U.S. DOT announced its ESV project, the aim of which was to obtain ...
presented passive seat belts.
Volvo The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...
tried to develop a passive three point seatbelt. In 1973, Volkswagen announced they had a functional passive seat belt. The first commercial car to use automatic seat belts was the 1975
Volkswagen Golf The Volkswagen Golf () is a compact car/small family car (C-segment) produced by the German automotive manufacturer Volkswagen since 1974, marketed worldwide across eight generations, in various body configurations and under various nameplates ...
. Automatic seat belts received a boost in the United States in 1977 when
Brock Adams Brockman Adams (January 13, 1927 – September 10, 2004) was an American lawyer and politician who served as a member of Congress. A Democrat from Washington, Adams served as a U.S. Representative, Senator, and United States Secretary of Trans ...
,
United States Secretary of Transportation The United States secretary of transportation is the head of the United States Department of Transportation. The secretary serves as the principal advisor to the president of the United States on all matters relating to transportation. The secre ...
in the Carter Administration, mandated that by 1983 every new car should have either airbags or automatic seat belts. There was strong lobbying against the passive restraint requirement by the auto industry. Adams was criticized by
Ralph Nader Ralph Nader (; born February 27, 1934) is an American political activist, author, lecturer, and attorney noted for his involvement in consumer protection, environmentalism, and government reform causes. The son of Lebanese immigrants to the Un ...
, who said that the 1983 deadline was too late. The
Volkswagen Rabbit The Volkswagen Golf () is a compact car/small family car (C-segment) produced by the German automotive manufacturer Volkswagen since 1974, marketed worldwide across eight generations, in various body configurations and under various nameplates ...
also had automatic seat belts, and VW said that by early 1978, 90,000 cars had sold with them. General Motors introduced a three-point non-motorized passive belt system in 1980 to comply with the passive restraint requirement. However, it was used as an active lap-shoulder belt because of unlatching the belt to exit the vehicle. Despite this common practice, field studies of belt use still showed an increase in wearing rates with this door-mounted system. General Motors began offering automatic seat belts on the
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. However, the company reported disappointing sales because of this feature. For the 1981 model year, the new
Toyota Cressida The is a compact, later mid-size sedan manufactured and marketed in Japan by Toyota between 1968 and 2004. Prior to 1972, the model was marketed as the Toyota Corona Mark II. In some export markets, Toyota marketed the vehicle as the Toyota Cres ...
became the first car to offer motorized automatic passive seatbelts. A study released in 1978 by the
United States Department of Transportation The United States Department of Transportation (USDOT or DOT) is one of the executive departments of the U.S. federal government. It is headed by the secretary of transportation, who reports directly to the President of the United States and ...
said that cars with automatic seat belts had a fatality rate of .78 per 100 million miles, compared with 2.34 for cars with regular, manual belts. In 1981,
Drew Lewis Andrew Lindsay Lewis Jr. (November 3, 1931 – February 10, 2016), generally known as Drew Lewis, was an American businessman and politician from the state of Pennsylvania. He was United States Secretary of Transportation in the first portion ...
, the first Transportation Secretary of the
Reagan Administration Ronald Reagan's tenure as the 40th president of the United States began with his first inauguration on January 20, 1981, and ended on January 20, 1989. Reagan, a Republican from California, took office following a landslide victory over D ...
, influenced by studies done by the auto industry, dropped the mandate; the decision was overruled in a
federal appeals court The United States courts of appeals are the intermediate appellate courts of the United States federal judiciary. The courts of appeals are divided into 11 numbered circuits that cover geographic areas of the United States and hear appeals fr ...
the following year, and then by the
Supreme Court A supreme court is the highest court within the hierarchy of courts in most legal jurisdictions. Other descriptions for such courts include court of last resort, apex court, and high (or final) court of appeal. Broadly speaking, the decisions of ...
. In 1984, the Reagan Administration reversed its course, though in the meantime the original deadline had been extended;
Elizabeth Dole Mary Elizabeth Alexander Hanford Dole (née Hanford; born July 29, 1936)Mary Ella Cathey Hanford, "Asbury and Hanford Families: Newly Discovered Genealogical Information" ''The Historical Trail'' 33 (1996), pp. 44–45, 49. is an American attorn ...
, then Transportation Secretary, proposed that the two passive safety restraints be phased into vehicles gradually, from vehicle model year 1987 to vehicle model year 1990, when all vehicles would be required to have either automatic seat belts or driver side air bags. Though more awkward for vehicle occupants, most manufacturers opted to use less expensive automatic belts rather than airbags during this time period. When driver side
airbags An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. T ...
became mandatory on all passenger vehicles in model year 1995, most manufacturers stopped equipping cars with automatic seat belts. Exceptions include the 1995–96 Ford Escort/
Mercury Tracer The Mercury Tracer is an automobile manurfactured and marketed by Ford's Mercury division for model years 1987-1999, over three generations in three- and five-door hatchback, four-door sedan, and five-door station wagon configurations. The firs ...
and the Eagle Summit Wagon, which had automatic safety belts along with dual airbags.


Systems

* Manual lap belt with automatic motorized shoulder belt—When the door is opened, the shoulder belt moves from a fixed point near the seat back on a track mounted in the door frame of the car to a point at the other end of the track near the windshield. Once the door is closed and the car is started, the belt moves rearward along the track to its original position, thus securing the passenger. The lap belt must be fastened manually. * Manual lap belt with automatic non-motorized shoulder belt—This system was used in American-market vehicles such as the
Hyundai Excel The Hyundai Excel (), also known as the Hyundai Pony, Hyundai Pony Excel, Hyundai Presto, Mitsubishi Precis and Hyundai X2, is an automobile which was produced by Hyundai Motor Company from 1985 to 2000. It was the first front-wheel drive car pr ...
and
Volkswagen Jetta The Volkswagen Jetta () is a compact car/small family car manufactured and marketed by Volkswagen since 1979. Positioned to fill a sedan niche above the firm's Golf hatchback, it has been marketed over seven generations, variously as the Atlant ...
. The shoulder belt is fixed to the aft upper corner of the vehicle door and is not motorized. The lap belt must be fastened manually. * Automatic shoulder and lap belts—This system was mainly used in General Motors vehicles, though it was also used on some
Honda Civic The is a series of automobiles manufactured by Honda since 1972. Since 2000, the Civic has been categorized as a compact car, while previously it occupied the subcompact class. , the Civic is positioned between the Honda Fit/City and Honda Acc ...
hatchbacks and
Nissan Sentra The Nissan Sentra is a series of automobiles manufactured by the Japanese automaker Nissan since 1982. Since 1999, the Sentra has been categorized as a compact car, while previously it occupied the subcompact class. Until 2006, Sentra was a reba ...
coupés. When the door is opened, the belts go from a fixed point in the middle of the car by the floor to the retractors on the door. Passengers must slide into the car under the belts. When the door closes, the seat belt retracts into the door. The belts have normal release buttons that are supposed to be used only in an emergency, but in practice are routinely used in the same manner as manual seat belt clasps. This system also found use by
American Specialty Cars American Specialty Cars (commonly known as ASC or American Sunroof Company) was an automobile supplier of highly engineered and designed roof systems, body systems and other specialty-vehicle systems for the world’s automakers. The company was ...
when they created the 1991-1994
convertible A convertible or cabriolet () is a passenger car that can be driven with or without a roof in place. The methods of retracting and storing the roof vary among eras and manufacturers. A convertible car's design allows an open-air driving expe ...
special edition of the
Nissan 240SX The Nissan 240SX is a sports compact car that was introduced to the North American market by Nissan in 1989 for the 1990 model year. It replaced the outgoing 200SX (S12) model. Most of the 240SXs were equipped with the 2.4-liter inline 4 engi ...
, a car that traditionally had a motorized shoulder belt.


Disadvantages

Automatic belt systems generally offer inferior occupant crash protection. In systems with belts attached to the door rather than a sturdier fixed portion of the vehicle body, a crash that causes the vehicle door to open leaves the occupant without belt protection. In such a scenario, the occupant may be thrown from the vehicle and suffer greater injury or death. Because many automatic belt system designs compliant with the US passive-restraint mandate did not meet the seatbelt anchorage requirements of
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
(CMVSS 210) — which were not weakened to accommodate automatic belts — vehicle models which had been eligible for easy importation in either direction across the US-Canada border when equipped with manual belts became ineligible for importation in either direction once the US variants obtained automatic belts and the Canadian versions retained manual belts. Two particular models affected were the
Dodge Spirit The Dodge Spirit is a mid-size 5- or 6-passenger sedan that was introduced in January 1989 as a replacement for the similarly sized Dodge 600. The Spirit was Dodge's version of the Chrysler AA platform, a stretched variation of the Chrysler K ...
and
Plymouth Acclaim The Plymouth Acclaim is a mid-size sedan produced in the 1989 to 1995 model years. The Acclaim was Plymouth's updated replacement for both the similarly sized E-body Caravelle and the K-body Reliant. Badge engineering was employed to give Dodge ...
. Automatic belt systems also present several operational disadvantages. Motorists who would normally wear seat belts must still fasten the manual lap belt, thus rendering redundant the automation of the shoulder belt. Those who do not fasten the lap belt wind up inadequately protected only by the shoulder belt. In a crash, without a lap belt, such a vehicle occupant is likely to "submarine" (be thrown forward under the shoulder belt) and be seriously injured. Motorized or door-affixed shoulder belts hinder access to the vehicle, making it difficult to enter and exit—particularly if the occupant is carrying items such as a box or a purse. Vehicle owners tend to disconnect the motorized or door-affixed shoulder belt to relieve the nuisance when entering and exiting the vehicle, leaving only a lap belt for crash protection. Also, many automatic seat belt systems are incompatible with child safety seats, or only compatible with special modifications.


Homologation and testing

Starting in 1971 and ending in 1972, the United States conducted a research project on seat belt effectiveness on a total of 40,000 vehicle occupants using car accident reports collected during that time. Of these 40,000 occupants, 18% were reported wearing lap belts, or two-point safety belts, 2% were reported wearing a three-point safety belt, and the remaining 80% were reported as wearing no safety belt. The results concluded that users of the two-point lap belt had a 73% lower fatality rate, a 53% lower serious injury rate, and a 38% lower injury rate than the occupants that were reported unrestrained. Similarly, users of the three-point safety belt had a 60% lower serious injury rate and a 41% lower rate of all other injuries. Out of the 2% described as wearing a three-point safety belt, no fatalities were reported. This study and others led to the Restraint Systems Evaluation Program (RSEP), started by the NHTSA in 1975 to increase the reliability and authenticity of past studies. A study as part of this program used data taken from 15,000 tow-away accidents that involved only car models made between 1973 and 1975. The study found that for injuries considered “moderate” or worse, individuals wearing a three-point safety belt had a 56.5% lower injury rate than those wearing no safety belt. The study also concluded that the effectiveness of the safety belt did not differ with the size of a car. It was determined that the variation among results of the many studies conducted in the 1960s and 70s was due to the use of different methodologies, and could not be attributed to any significant variation in the effectiveness of safety belts.
Wayne State University Wayne State University (WSU) is a public research university in Detroit, Michigan. It is Michigan's third-largest university. Founded in 1868, Wayne State consists of 13 schools and colleges offering approximately 350 programs to nearly 25,000 ...
’s Automotive Safety Research Group, as well as other researchers, are testing ways to improve seat belt effectiveness and general vehicle safety apparatuses. Wayne State’s Bioengineering Center uses human
cadavers A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...
in their crash test research. The Center’s director, Albert King, wrote in 1995 that the vehicle safety improvements made possible since 1987 by the use of cadavers in research had saved nearly 8,500 lives each year, and indicated that improvements made to three-point safety belts save an average of 61 lives every year. The
New Car Assessment Program A New Car Assessment Program (or Programme) is a government car safety program tasked with evaluating new automobile designs for performance against various safety threats. History The first NCAP was created in 1979, by the United States Nation ...
(NCAP) was put in place by the United States National Highway Traffic Safety Administration in 1979. The NCAP is a government program that evaluates vehicle safety designs and sets standards for foreign and domestic automobile companies. The agency developed a rating system and requires access to safety test results. , manufacturers are required to place an NCAP star rating on the automobile price sticker. In 2004, The European New Car Assessment Program (
Euro NCAP The European New Car Assessment Programme (Euro NCAP) is a European voluntary car safety performance assessment programme (i.e. a New Car Assessment Program) based in Leuven (Belgium) formed in 1996, with the first results released in February ...
), started testing seat belts and whiplash safety on all test cars at the Thatcham Research Centre with crash test dummies.


Experimental

Research and development efforts are ongoing to improve the safety performance of vehicle seatbelts. Some experimental designs include: *''Criss-cross'' Experimental safety belt presented in the
Volvo SCC The Volvo Safety Concept Car (SCC) is an ESV concept car which was first shown at the 2001 North American International Auto Show in Detroit, Michigan. The SCC incorporates the rear hatch design from Volvo P1800ES and the glass hatch from Volv ...
. It forms a cross-brace across the chest. * ''3+2 Point Seatbelt'': Experimental safety belt from Autoliv similar to the criss-cross. The 3+2 improves protection against rollovers and side impacts. * ''Four point'' ''"belt and suspenders"'': An experimental design from Ford where the "suspenders" are attached to the backrest, not to the frame of the car. * 3 point Adjustable Seatbelt: Experimental safety belt fro
GWR Safety Systems
that allowed the car
Hiriko The Hiriko is a folding two-seat urban electric car that was under development by the Hiriko Driving Mobility consortium in the Basque Country of northern Spain. The electric car was to be the commercial implementation of the CityCar project dev ...
, designed by MIT, to fold without compromising the safety and comfort of the occupants.


In rear seats

In 1955 (as a 1956 package), Ford offered lap only seat belts in the rear seats as an option within the ''Lifeguard'' safety package. In 1967, Volvo started to install lap belts in the rear seats. In 1972, Volvo upgraded the rear seat belts to a three-point belt. In crashes, unbelted rear passengers increase the risk of belted front seat occupants' death by nearly five times.


Child occupants

As with adult drivers and passengers, the advent of seat belts was accompanied by calls for their use by child occupants, including legislation requiring such use. Generally, children using adult seat belts suffer significantly lower injury risk when compared to non-buckled children. The UK extended compulsory seatbelt wearing to child passengers under the age of 14 in 1989. It was observed that this measure was accompanied by a 10% ''increase'' in fatalities and a 12% ''increase'' in injuries among the target population. In crashes, small children who wear adult seatbelts can suffer "seat-belt syndrome" injuries including severed intestines, ruptured diaphragms, and spinal damage. There is also research suggesting that children in inappropriate restraints are at significantly increased risk of head injury, one of the authors of this research said, "The early graduation of kids into adult lap and shoulder belts is a leading cause of child-occupant injuries and deaths." As a result of such findings, many jurisdictions now advocate or require child passengers to use specially designed child restraints. Such systems include separate child-sized seats with their own restraints and booster cushions for children using adult restraints. In some jurisdictions, children below a certain size are forbidden to travel in front car seats."


Automated reminders and engine start interlocks

In Europe, the US, and some other parts of the world, most modern cars include a seat-belt reminder light for the driver and some also include a reminder for the passenger, when present, activated by a pressure sensor under the passenger seat. Some cars will intermittently flash the reminder light and sound the chime until the driver (and sometimes the front passenger, if present) fasten their seatbelts. In 2005, in Sweden, 70% of all cars that were newly registered were equipped with seat belt reminders for the driver. Since November 2014, seat belt reminders are mandatory for the driver's seat on new cars sold in Europe. Two specifications define the standard of seat belt reminder: UN Regulation 16, Section 8.4 and the Euro NCAP assessment protocol (Euro NCAP, 2013).


US regulation history

The Federal Motor Vehicle Safety Standard № 208 (FMVSS 208) was amended by the NHTSA to require a seat belt/starter interlock system to prevent passenger cars from being started with an unbelted front-seat occupant. This mandate applied to passenger cars built after August 1973, i.e., starting with the 1974
model year The model year (sometimes abbreviated "MY") is a method of describing the version of a product which has been produced over multiple years. The model year may or may not be the same as the calendar year in which the product was manufactured. ...
. The specifications required the system to permit the car to be started only if the belt of an occupied seat were fastened after the occupant sat down, so pre-buckling the belts would not defeat the system. The interlock systems used logic modules complex enough to require special diagnostic computers, and were not entirely dependable—an override button was provided under the hood of equipped cars, permitting one (but only one) "free" starting attempt each time it was pressed. However, the interlock system spurred severe backlash from an American public who largely rejected seat belts. In 1974, Congress acted to prohibit NHTSA from requiring or permitting a system that prevents a vehicle from starting or operating with an unbelted occupant, or that gives an audible warning of an unfastened belt for more than 8 seconds after the ignition is turned on. This prohibition took effect on 27 October 1974, shortly after the 1975 model year began. In response to the Congressional action, NHTSA once again amended FMVSS 208, requiring vehicles to come with a seat belt reminder system that gives an audible signal for 4 to 8 seconds and a warning light for at least 60 seconds after the ignition is turned on if the driver's seat belt is not fastened. This is called a seat belt reminder (SBR) system. In the mid-1990s, the Swedish insurance company Folksam worked with Saab and Ford to determine the requirements for the most efficient seat belt reminder. One characteristic of the optimal SBR, according to the research, is that the audible warning becomes increasingly penetrating the longer the seat belt remains unfastened.


Efficacy

In 2001, Congress directed NHSTA to study the benefits of technology meant to increase the use of seat belts. NHSTA found that seat belt usage had increased to 73% since the initial introduction of the SBR system. In 2002, Ford demonstrated that seat belts were used more in Fords with seat belt reminders than in those without: 76% and 71% respectively. In 2007, Honda conducted a similar study and found that 90% of people who drove Hondas with seat belt reminders used a seat belt, while 84% of people who drove Hondas without seat belt reminders used a seat belt. In 2003, the Transportation Research Board Committee, chaired by two psychologists, reported that "Enhanced SBRs" (ESBRs) could save an additional 1,000 lives a year. Research by the Insurance Institute for Highway Safety found that Ford's ESBR, which provides an intermittent chime for up to five minutes if the driver is unbelted, sounding for 6 seconds then pausing for 30, increased seat belt use by 5 percentage points. Farmer and Wells found that driver fatality rates were 6% lower for vehicles with ESBR compared with otherwise-identical vehicles without.


Delayed start

Starting with the 2020 model year, some
Chevrolet Chevrolet ( ), colloquially referred to as Chevy and formally the Chevrolet Motor Division of General Motors Company, is an American automobile division of the American manufacturer General Motors (GM). Louis Chevrolet (1878–1941) and ous ...
cars will refuse to shift from Park to Drive for 20 seconds if the driver is unbuckled and the car is in "teen driver" mode. A similar feature was previously available on some General Motors fleet cars.


Regulation by country


International regulations

Several countries apply UN-ECE
vehicle regulation Vehicle regulations are requirements that automobiles must satisfy in order to be approved for sale or use in a particular country or region. They are usually mandated by legislation, and administered by a government body. The regulations concern a ...
s 14 and 16: * UN Regulation No. 14: safety belt anchorages * UN Regulation No. 16: ** Safety belts, restraint systems, child restraint systems, and ISOFIX child restraint systems for occupants of power-driven vehicles ** Vehicles equipped with safety belts, safety belt reminders, restraint systems, child restraint systems and ISOFIX child restraint systems and i-Size child restraint systemshttps://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2020/ECE-TRANS-WP.29-343-Rev.28-Add.1.pdf * UN Regulation No. 44: restraining devices for child occupants of power-driven vehicles ("Child Restraint Systems") * UN Regulation No. 129: Enhanced Child Restraint Systems


Local regulations


Legislation

Observational studies of car crash morbidity and mortality,
experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into Causality, cause-and-effect by demonstrating what outcome oc ...
s using both
crash test dummies Crash Test Dummies are a Canadian rock band from Winnipeg, Manitoba. The band is most identifiable through Brad Roberts (vocals, guitar) and his distinctive bass-baritone voice. The band members have fluctuated over the years, but its best kno ...
and human
cadaver A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...
s indicate that wearing seat belts greatly reduces the risk of
death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
and injury in the majority of car crashes. This has led many countries to adopt mandatory seat belt wearing laws. It is generally accepted that, in comparing like-for-like accidents, a vehicle occupant not wearing a properly fitted seat belt has a significantly and substantially higher chance of death and serious injury. One large observation studying using US data showed that the
odds ratio An odds ratio (OR) is a statistic that quantifies the strength of the association between two events, A and B. The odds ratio is defined as the ratio of the odds of A in the presence of B and the odds of A in the absence of B, or equivalently (due ...
of crash death is 0.46 with a three-point belt when compared with no belt. In another study that examined injuries presenting to the ER pre- and post-seat belt law introduction, it was found that 40% more escaped injury and 35% more escaped mild and moderate injuries. The effects of seat belt laws are disputed by those who observe that their passage did not reduce road fatalities. There was also concern that instead of legislating for a general protection standard for vehicle occupants, laws that required a particular technical approach would rapidly become dated as motor manufacturers would tool up for a particular standard that could not easily be changed. For example, in 1969 there were competing designs for lap and three-point seat belts, rapidly tilting seats, and airbags being developed. As countries started to mandate seat belt restraints the global auto industry invested in the tooling and standardized exclusively on seat belts, and ignored other restraint designs such as airbags for several decades As of 2016, seat belt laws can be divided into two categories: primary and secondary. A primary seat belt law allows an officer to issue a citation for lack of seatbelt use without any other citation, whereas a secondary seat belt law allows an officer to issue a seat belt citation only in the presence of a different violation. In the United States, fifteen states enforce secondary laws, while 34 states, as well as the District of Columbia, American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands, enforce primary seat belt laws. New Hampshire lacks both a primary and secondary seat belt law.


Risk compensation

Some have proposed that the number of deaths was influenced by the development of
risk compensation Risk compensation is a theory which suggests that people typically adjust their behavior in response to perceived levels of risk, becoming more careful where they sense greater risk and less careful if they feel more protected. Although usually ...
, which says that drivers adjust their behavior in response to the increased sense of personal safety wearing a seat belt provides. In one trial subjects were asked to drive
go-kart A go-kart, also written as go-cart (often referred to as simply a kart), is a type of sports car, close wheeled car, open-wheel car or quadracycle. Go-karts come in all shapes and forms, from non-motorised models to high-performance Kart rac ...
s around a track under various conditions. It was found that subjects who started driving unbelted drove consistently faster when subsequently belted. Similarly, a study of habitual non-seatbelt wearers driving in freeway conditions found evidence that they had adapted to seatbelt use by adopting higher driving speeds and closer following distances. A 2001 analysis of US crash data aimed to establish the effects of seatbelt legislation on driving fatalities and found that previous estimates of seatbelts effectiveness had been significantly overstated. According to the analysis, seatbelts decreased fatalities by 1.35% for each 10% increase in seatbelt use. The study controlled for endogenous motivations of seat belt use, because that creates an artificial correlation between seat belt use and fatalities, leading to the conclusion that seatbelts cause fatalities. For example, drivers in high-risk areas are more likely to use seat belts and are more likely to be in accidents, creating a non-causal correlation between seatbelt use and mortality. After accounting for the endogeneity of seatbelt usage, Cohen and Einav found no evidence that the risk compensation effect makes seatbelt-wearing drivers more dangerous, a finding at variance with other research.


Increased traffic

Other statistical analyses have included adjustments for factors such as increased traffic and age, and based on these adjustments, which results in a reduction of morbidity and mortality due to seat belt use. However,
Smeed's law Smeed's Law is an empirical rule suggested to relate traffic fatalities to traffic congestion as measured by the proxy of motor vehicle registrations and country population. The law proposes that increasing traffic volume (an increase in motor ...
predicts a fall in accident rate with increasing car ownership and has been demonstrated independently of seat belt legislation.


Mass transit considerations


Buses


School buses

In the US, six states—California, Florida, Louisiana, New Jersey, New York, and Texas—require seat belts on school buses. Pros and cons had been alleged about the use of seatbelts in school buses. School buses, which are much bigger in size than the average vehicle, allow for the mass transportation of students from place to place. The American School Bus Council states in a brief article saying that, "The children are protected like eggs in an egg carton—compartmentalized, and surrounded with padding and structural integrity to secure the entire container." (ASBC). Although school buses are considered safe for mass transit of students this will not guarantee that the students will be injury-free if an impact were to occur. Seatbelts in buses are sometimes believed to make recovering from a roll or tip harder for students and staff as they could be easily trapped in their own safety belts. In 2015, for the first time, NHTSA endorsed seat belts on school buses.


Motor coaches

In the European Union, all new long-distance buses and coaches must be fitted with seat belts. Australia has required lap/sash seat belts in new coaches since 1994. These must comply with Australian Design Rule 68, which requires the seat belt, seat and seat anchorage to withstand 20 g deceleration and an impact by an unrestrained occupant to the rear. In the United States, NHTSA has now required lap-shoulder seat belts in new "over-the-road" buses (includes most coaches) starting in 2016.


Trains

The use of seatbelts in trains has been investigated. Concerns about survival space intrusion in train crashes and increased injuries to unrestrained or incorrectly restrained passengers led the researchers to discourage the use of seat belts in trains. :"It has been shown that there is no net safety benefit for passengers who choose to wear 3-point restraints on passenger-carrying rail vehicles. Generally, passengers who choose not to wear restraints in a vehicle modified to accept 3-point restraints receive marginally more severe injuries."


Airplanes

All aerobatic aircraft and gliders (sailplanes) are fitted with four or five-point harnesses, as are many types of light aircraft and many types of military aircraft. The seatbelts in these aircraft have the dual function of crash protection and keeping the pilot(s) and crew in their seat(s) during turbulence and aerobatic maneuvers. Passenger aircraft are fitted with lap belts. Unlike road vehicles, passenger aircraft seat belts are not primarily designed for crash protection. In fact, their main purpose is to keep passengers in their seats during events such as turbulence. Many
civil aviation Civil aviation is one of two major categories of flying, representing all non-military and non-state aviation, both private and commercial. Most of the countries in the world are members of the International Civil Aviation Organization and work ...
authorities require a "fasten seat belt" sign in passenger aircraft that can be activated by a pilot during takeoff, turbulence, and landing. The
International Civil Aviation Organization The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sc ...
recommends the use of child restraints. Some airline authorities, including the UK Civil Aviation Authority (CAA), permit the use of airline infant lap belts (sometimes known as an infant loop or belly belt) to secure an infant under two sitting on an adults lap.


See also

*
Automobile safety Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design. ...
*
Baby transport Various methods of transporting children have been used in different cultures and times. These methods include baby carriages (prams in British English), infant car seats, portable bassinets (carrycots), strollers (pushchairs), slings, backpack ...
*
Crashworthiness Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different crit ...
* Passive safety device *
Safety harness A safety harness is a form of protective equipment Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards a ...
*
Seat belt use rates by country This is a table of seat belt use rates (percent) in various countries worldwide. Seat belt use rates metrics might be part of some safety process. See also * Seat belt legislation * Seat belt use rates in the United States Seat belt use rat ...


References


External links

* {{Authority control Vehicle safety technologies English inventions Safety equipment Seat belts Vehicle parts