A seat belt, also known as a safety belt, is a vehicle safety device designed to secure the occupant of a vehicle against harmful movement that may result during a ...
History
Seat belts were invented by English engineer
George Cayley in the mid-19th century,
[3] though Edward J. Claghorn of New York, was granted the first patent (
U.S. Patent 312,085, on February 10, 1885 for a safety belt).
[4]
Claghorn was granted United States Patent #312,085 for a Safety-Belt
for tourists, painters, firemen, etc. who are being raised or lowered,
described in the patent as "designed to be applied to the person, and
provided with hooks and other attachments for securing the person to a
fixed object."
In 1911,
Benjamin Foulois had the cavalry
saddle
shop fashion a belt for the seat of Wright Flyer Signal Corps 1. He
wanted it to hold him firmly in his seat so he could better control his
aircraft as he bounded along the rough field used for takeoff and
landing. It was not until
World War II
that seat belts were fully adopted in military aircraft, and even then,
it was mainly for safety reasons, not improved aircraft control.
[citation needed]
In 1946, Dr. C. Hunter Shelden had opened a neurological practice at Huntington Memorial Hospital in
Pasadena, California.
In the early 1950s, Dr. Shelden had made a major contribution to the
automotive industry with his idea of retractable seat belts. This came
about greatly in part from the high number of head injuries coming
through the emergency rooms.
[5]
He investigated the early seat belts whose primitive designs were
implicated in these injuries and deaths. His findings were published in
the November 5, 1955
Journal of the American Medical Association (JAMA) in which he proposed not only the retractable seat belt, but also recessed
steering wheels, reinforced roofs,
roll bars, door locks and passive restraints such as the
air bag. Subsequently, in 1959, Congress passed legislation requiring all automobiles to comply with certain safety standards.
[6]
American car manufacturers
Nash (in 1949) and Ford (in 1955) offered seat belts as options, while Swedish
Saab first introduced seat belts as standard in 1958.
[7] 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.
[8]
Glenn Sheren of Mason, Michigan submitted a patent application on
March 31, 1955 for an automotive seat belt and was awarded US Patent
2,855,215 in 1958. This was a continuation of an earlier patent
application that Mr. Sheren had filed on September 22, 1952.
[9]
However, the first modern three point seat belt (the so-called
CIR-Griswold restraint) used in most consumer vehicles today was patented in 1955
U.S. Patent 2,710,649 by the Americans Roger W. Griswold and
Hugh DeHaven,
[10] and developed to its modern form by Swedish inventor
Nils Bohlin for Swedish manufacturer
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.
[11] Bohlin was granted
U.S. Patent 3,043,625 for the device.
[7]
The world's first seat belt law was put in place in 1970, in the state of
Victoria, Australia,
making the wearing of a seat belt compulsory for 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.
[12]
Types
Two-point
A 2-point belt attaches at its two endpoints, and was invented in the early 1900s by
Jack Swearingen of
Louisville, Kentucky.
Lap
A lap ("2-point") belt in an airplane
A lap belt is a strap that goes over the waist. This was the most
commonly installed type of belt prior to legislation requiring 3-point
belts, and is primarily found in older cars.
Coaches 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 on the automatic retractable lap safety
belt.
Ralph Nader cited Ryan's work in
Unsafe at Any Speed and in 1966 President
Lyndon Johnson signed two bills requiring safety belts in all passenger vehicles starting in 1968.
[13]
Until the 1980s, three-point belts were commonly available only in
the front outboard seats of cars; the back seats were only often fitted
with lap belts. Evidence of the potential of lap belts to cause
separation of the
lumbar vertebrae and the sometimes associated
paralysis,
or "seat belt syndrome", led to progressive revision of passenger
safety regulations in nearly all developed countries to require 3-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 U.S. require a lap and shoulder belt in the center
rear seat.
[14] Besides regulatory changes, "seat belt syndrome" has led to tremendous
liability for vehicle manufacturers. One Los Angeles case resulted in a $45 million jury verdict against the
Ford Motor Company;
the resulting $30 million judgment (after deductions for another
defendant who settled prior to trial) was affirmed on appeal in 2006.
[15]
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 U.S.
National Highway Traffic Safety Administration's
Federal Motor Vehicle Safety Standard 208 on 1 January 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, 3-point belt
systems such as
Chrysler's
"Uni-Belt" began to supplant the separate lap and shoulder belts in
American-made cars, though such 3-point belts had already been supplied
in European vehicles such as
Volvos,
Mercedes, and
Saabs for some years.
Three-point
A 3-point belt is a
Y-shaped arrangement, similar to the
separate lap and sash belts, but unitized. Like the separate
lap-and-sash belt, in a collision the 3-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.
[16] The first car with a three-point belt was a
Volvo PV 544
that was delivered to a dealer in Kristianstad on August 13, 1959.
However, the first car model to feature the three-point seat belt as a
standard item was the 1959
Volvo 122, first outfitted with a two-point belt at initial delivery in 1958, replaced with the three-point seat belt the following year.
[17] The three-point belt was developed by
Nils Bohlin who had earlier also worked on
ejection seats at
Saab.
[18]
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.
[19][20]
Belt-in-Seat (BIS)
The 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. Fitment was standard on the front seats from 1970.
[21] Some cars like the
Renault Vel Satis
use this system for the front seats. A General Motors assessment
concluded seat-mounted 3-point belts offer better protection especially
to smaller vehicle occupants,
[22] though GM did not find a safety performance improvement in vehicles with seat-mounted belts versus body-mounted belts.
[23]
BIS 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.
[citation needed]
4-, 5-, and 6-point
Five-point harnesses are typically found in
child safety seats and in
racing cars. The lap portion is connected to a belt between the
legs
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 6-point harness became popular after the
death of Dale Earnhardt,
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.
[24]
Seven-point
Aerobatic aircraft
frequently use a combination harness consisting of a five-point harness
with a redundant lap-belt attached to a different part of the air
craft. 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.
Technology
Seat belt with uncovered inertial reel
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. Most modern seat belts are stowed on spring-loaded
reels called "retractors" equipped with
inertial
locking mechanisms that stop the belt from extending off the reel
during severe deceleration. There are two main types of inertial seat
belt lock. A webbing-sensitive lock is based on a
centrifugal clutch
activated by 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.
A vehicle-sensitive lock is based on a
pendulum
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
Pyrotechnic pretensioner diagram
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 reducing injury in the event an actual collision occurs.
[25]
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 clamp 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 a 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 3-point restraints
fitted with pyrotechnic or electric pretensioners were not able to
eliminate all interior passenger compartment head strikes in rollover
test conditions.
[26] Electric pretensioners are often incorporated on vehicles equipped with
precrash systems;
they are designed to reduce seat belt slack in a potential collision
and assist in placing the occupants in a more optimal seating position.
[27]
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.
[28]
Inflatable seatbelts have tubular inflatable bladders contained within
an outer cover. When a crash occurs the bladder inflates with a 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.
[29]
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 and
Flex.
[30]
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 first car to feature automatic shoulder belts as standard equipment was the 1981
Toyota Cressida, but the history of such belts goes back further.
[31]
The 1972
Volkswagen ESVW1
Experimental Safety Vehicle presented passive seat belts.
[32] Volvo tried to develop a passive three point seatbelt. In 1973 Volkswagen announced they had a functional passive seat belt.
[33] The first commercial car to use automatic seat belts was the 1975
Volkswagen Rabbit.
[34]
Automatic seat belts received a boost in the
United States in 1977 when
Brock Adams,
United States Secretary of Transportation in the
Carter Administration, mandated that by 1983 every new car should have either
airbags or automatic seat belts
[35][36] despite strong lobbying from the auto industry.
[37] Adams was attacked by
Ralph Nader, who said that the 1983 deadline was too late.
[38] Soon after,
General Motors began offering automatic seat belts, first on the
Chevrolet Chevette,
[39][40] but by early 1979 the VW Rabbit and the Chevette were the only cars to offer the safety feature,
[38] and GM was reporting disappointing sales.
[41] By early 1978, Volkswagen had reported 90,000 Rabbits sold with automatic seat belts.
[34] A study released in 1978 by the
United States Department of Transportation
claimed 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.
[42]
In 1981,
Drew Lewis, the first Transportation Secretary of the
Reagan Administration, influenced by studies done by the auto industry,
[43] "killed"
[44] the previous administration's mandate;
[45] the decision was overruled in a
federal appeals court the following year,
[46] and then by the
Supreme Court.
[44] In 1984, the Reagan Administration reversed its course,
[47] though in the meantime the original deadline had been extended;
Elizabeth Dole,
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.
[44]
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
became mandatory on all passenger vehicles in model year 1995, most
manufacturers stopped equipping cars with automatic seat belts.
Exceptions include the 1995-1996
Ford Escort/
Mercury Tracer and the
Eagle Summit Wagon which had automatic safety belts along with dual airbags.
[citation needed]
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 and Volkswagen Jetta.
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 hatchbacks and Nissan Sentra
coupés. When the door is opened, the belts go from a fixed point in the
middle of the car by the floor to 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.[citation needed]
Disadvantages
Automatic belt systems generally offer inferior occupant crash protection.
[48][49]
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.
[49]
Because many automatic belt system designs compliant with the US
passive-restraint mandate did not meet the safety performance
requirements of
Canada—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 got automatic belts
and the Canadian versions retained manual belts. Two such models were
the
Dodge Spirit and
Plymouth Acclaim.
[50][51]
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 by only 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 alleviate the nuisance of
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 compatible only with special modifications.
Experimental
Research and development efforts are ongoing to improve the safety
performance of vehicle seatbelts. Some experimental designs have
included:
- Criss-cross Experimental safety belt presented in the Volvo SCC. It forms a cross-brace across the chest.[23]
- 3+2 Point Seatbelt: Experimental safety belt from Autoliv similar to the criss-cross. The 3+2 improves protection against rollovers and side impacts.[52]
- 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.[53]
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.
[54]
In crashes, unbelted rear passengers increase the risk of belted front seat occupants' death by nearly five times.
[55][56]
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.
[57]
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,
[58]
one of the authors of this research has been quoted as claiming that:
"The early graduation of kids into adult lap and shoulder belts is a
leading cause of child-occupant injuries and deaths."
[59]
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."
[60]
Reminder chime and light
Examples of warning lights on a car dashboard.
In Europe 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.
[citation needed]
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.
[citation needed]
In North America, cars sold since the early 1970s
[vague] have included an audiovisual reminder system consisting of a
tell-tale light
on the dashboard and a buzzer or chime reminding the driver and
passengers to fasten their belts. Originally, these lights were
accompanied by a warning buzzer whenever the transmission was in any
position except park if either the driver was not buckled up or, as
determined by a pressure sensor in the passenger's seat, if there was a
passenger there not buckled up.
[citation needed]
However, this was considered by many to be a major annoyance, as the
light would be on and the buzzer would sound continuously if front-seat
passengers were not buckled up. Therefore, people who did not wish to
buckle up would defeat this system by fastening the seat belts with the
seat empty and leaving them that way.
[citation needed]
To combat this dangerous habit, in 1971
[citation needed] NHTSA amended
Federal Motor Vehicle Safety Standard № 208
(FMVSS 208) 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 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.
[61][62]
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.
[63]
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.
[62] This prohibition took effect on 27 October 1974, shortly after the 1975 model year began.
[64]
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.
[62] This is called a
seat belt reminder
(SBR) system. In the mid-1990s, an insurance company from Sweden called
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.
[65]
In 2003, the Transportation Research Board Committee, chaired by two
psychologists, reported that ESBRs could save an additional 1,000 lives a
year.
[66]
Research by the Insurance Institute for Highway Safety found that
Ford's ESBR, which provides an intermittent chime intermittently for up
to five minutes if the driver is unbelted, sounding for 6 seconds then
pausing for 30, increased seat belt use by 5 percent.
[66]
Farmer and Wells found that driver fatality rates were 6% lower for
vehicles with ESBR compared with otherwise-identical vehicles without.
[67]
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.
[62]
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.
[65]
Legislation
Observational studies of
car crash morbidity and mortality,
[68][69][70] experiments using both
crash test dummies and human
cadavers indicate that wearing seat belts greatly reduces the risk of
death 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 of crash death is 0.46 with a three-point belt, when compared with no belt.
[71] 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.
[72]
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 which could not easily be changed. For example, in
1969 there were competing designs for lap and 3-point seat belts,
rapidly tilting seats, and
air bags
being developed. But 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 air bags for several decades
[73]
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 and 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.
[74]
Risk compensation
Some have proposed that the number of deaths was influenced by the development of
risk compensation,
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-karts
around a track under various conditions. It was found that subjects who
started driving unbelted drove consistently faster when subsequently
belted.
[75]
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.
[76] A 2001 analysis of US crash data aimed to establish the effects of seatbelt legislation on driving fatalities
[77]
and found that previous estimates of seatbelts effectiveness had been
significantly overstated. According to the analysis used, seatbelts were
claimed to have decreased fatalities by 1.35% for each 10% increase in
seatbelt use. The study controlled for endogenous motivations of seat
belt use, which it is claimed 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 other factors such as age, and based on these
adjustments, a reduction of morbidity and mortality due to seat belt
use has been claimed.
[68] However,
Smeed's law
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
Pros
[78][79][80] and cons
[81][82][83]
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 the school is 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 would make recovering
from a roll or tip harder for students and staff as they could be easily
trapped in their own safety belt.
[84]
Motor coaches
In the European Union, all new long distance buses and coaches must be fitted with seat belts.
[85]
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 20g deceleration and an
impact by an unrestrained occupant to the rear.
[86]
In the United States, NHTSA has now required lap-shoulder seat belts
in new "over-the-road" buses (includes most coaches) starting in 2016.
[87]
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."[88]
Airplanes
Many
civil aviation authorities require a "fasten seat belt" sign in passenger aircraft that can be activated by a pilot during turbulence.
[89][90] The
International Civil Aviation Organization recommends the use of child restraints.
[91]
See also
References
A lap belt is a strap that goes over the waist. This was the most commonly installed type of belt prior to legislation requiring 3-point belts, and is primarily found in older cars. Coaches are equipped with lap belts (although many newer coaches have three-point belts), as are passenger aircraft seats.A lap ("2-point") belt in an airplane
A 3-point belt is a Y-shaped arrangement, similar to the separate lap and sash belts, but unitized. Like the separate lap-and-sash belt, in a collision the 3-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.[16] The first car with a three-point belt was a Volvo PV 544 that was delivered to a dealer in Kristianstad on August 13, 1959. However, the first car model to feature the three-point seat belt as a standard item was the 1959 Volvo 122, first outfitted with a two-point belt at initial delivery in 1958, replaced with the three-point seat belt the following year.[17] The three-point belt was developed by Nils Bohlin who had earlier also worked on ejection seats at Saab.[18] 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.[19][20]A 3-point seat belt
Five-point harnesses are typically found in child safety seats and in racing cars. The lap portion is connected to a belt between the legs 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 6-point harness became popular after the death of Dale Earnhardt, 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.[24]Bucket seat combined with a Schroth 6-point harness in a 2010 Porsche 997 GT3 RS 3.8
Seat belt with uncovered inertial reel
Seatbelts in many newer vehicles are also equipped with "pretensioners" or "web clamps", or both.Pyrotechnic pretensioner diagram
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 first car to feature automatic shoulder belts as standard equipment was the 1981 Toyota Cressida, but the history of such belts goes back further.[31]Automatic seat belt in a Honda Civic![[icon]](https://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/20px-Wiki_letter_w_cropped.svg.png)
In Europe 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.[citation needed] 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.[citation needed]Examples of warning lights on a car dashboard.
![[icon]](https://en.wikipedia.org/wiki/File:Wiki_letter_w_cropped.svg){kind=small}
Media related to Seat belts at Wikimedia Commons
No comments:
Post a Comment