Seatbelts

=​​​​ Seat Belts = Main

Fact sheet from the National Highway Traffic Safety Administration (NHTSA): [|Seat belt Fact Sheet]

Timeline: media type="custom" key="6280415" align="center" > New York considers and rejects a bill requiring seat belts installed in all new cars sold in state > Wisconsin requires seat belts in front seats
 * 1849 - Volvo invents first safety belts
 * 1885 - First US Patent for Automobile Seat belts given to Edward J. Claghorn
 * 1910 - "lap-belt" resembling modern seat-belts first installed in a US Army Airplane
 * 1930s - Doctors begin installing seat belts in their own cars; They urge manufacturers to put them in all cars.
 * 1950s - Seat belts were being installed in cars by manufacturers
 * 1955 - California required state approval of all seat belts before use or sale
 * 1959 - Volvo invents 3 pt seat belt
 * 1960 - New York considers and rejects the bill again
 * 1961 - New York requires seat belt anchors in the front seats of all new cars
 * 1965 - All manufacturers install lap belts in front seats
 * 1969 - Volvo provides 3 pt seat belts in rear seats
 * By the 1970s - 3 pt seat belt became the common type of seat belt used in cars
 * 1974 - the National Highway Traffic Safety Administration (NHTSA) requires 3 pt seat belts in the front seats of cars
 * 1985 - New York makes seat belt use mandatory both in front and rear seats.

= = = = = = = = =General information:=

Seat belts are intended to both keep passengers in their seats and to attempt to keep the sum of the forces acting on the body as close to zero as possible, thus reducing the likelihood of serious injuries.

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(Video from Archive.org {public domain})

=Legislation:=

§ 406. Safety belt performance grants (a) In general.--The Secretary shall make grants to States in accordance with the provisions of this section to encourage the enactment and enforcement of laws requiring the use of safety belts in passenger motor vehicles.
 * This is the federal government refusing to give money to states unless they make laws requiring seat belts usage. Since the federal government has no direct power in this area, they take an indirect path to get their legislation across. This is also a safety net that prevents anyone from suing them on grounds of unconstitutionality.
 * In 2002, 48 states (all except Wyoming and Maine), D.C, and Puerto Rico shared $44 million in federal grant money for safety and awareness campaigns.


 * Map of Seat Belt Laws By State**



States with Primary Seat Belt Laws States with Secondary Seat Belt Laws


 * Primary seat belt laws - Can get pulled over and issued a ticket just for not wearing a seat belt
 * 30 states (Alabama, Alaska, Arkansas, California, Connecticut, Delaware, Florida, Georgia (except pick-up truck drivers), Hawaii, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Michigan, Minnesota, Mississippi, New Jersey [secondary offense for rear seats], New Mexico, New York, North Carolina [secondary offense for rear seats], Oklahoma, Oregon, South Carolina, Tennessee, Texas, Washington, Wisconsin)
 * Washington D.C
 * Territories (American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands)
 * Secondary Seat Belt Laws - Have to be pulled over for a different "citable" offense and may be ticketed for not wearing a seat belt
 * 19 states (Arizona, Colorado, Idaho, Kansas [ages 14 - 17, primary offense], Massachusetts, Missouri [ages 8 - 15, primary offense], Montana, Nebraska, Nevada, North Dakota, Ohio, Pennsylvania, Rhode Island [< age 18, primary offense], South Dakota, Utah[ < age 19, primary offense], Vermont [ < age 18, primary offense], Virginia, West Virginia, Wyoming)
 * Only state without either a primary or secondary law - New Hampshire

Primary Enforcement
Section 4581 (a)(3) Restraint Systems FINE: $10.00 plus CAT, EMS, and JCP- no court costs assessed. This varies from state to state. It ranges from $10 in Wisconsin to $100 in Guam and North Carolina. 
 * A driver who is under 18 may not operate a motor vehicle in which the number of passengers exceeds the number of available seat belts in the vehicle. (Primary)

Secondary Enforcement
Section 4581 (a)(2) Restraint Systems FINE: $10.00 plus CAT, EMS and JCP when convicted of a primary offense. This also varies from state to state. It ranges from $10 in Pennsylvania and Missouri and for passengers in Wyoming to $75 in Rhode Island. 
 * Driver and all front seat passengers must be restrained.
 * Drivers are responsible for themselves and to secure all children from 8 years of age up to 18 years of age in a seat belt system any where in the vehicle.
 * Exemptions include carriers of medical or psychological excuses signed by a physician, rural letter carriers, deliverers of goods or service vehicle operators driving at speeds less than 15 mph and making frequent stops, drivers, and front seat passengers of automobiles manufactured before July 1, 1966.

Primary Enforcement
Section 4581 (a)(1) Restraint Systems FINE: Maximum fine of $100.00 plus court costs, CAT, EMS, JCP or proof of car seat purchase. 
 * All drivers are responsible to secure children from birth to age 4 in an approved child passenger restraint system.

Secondary Enforcement
Section 4581 (a)(1.l)
 * All drivers are responsible to secure children from 4 years of age up to 8 years of age in a seat belt system and an appropriately fitting child booster seat.
 * Exemptions are allowed under the law. -

Resistance to Legislation:
The resistance to legislation regarding seat belts stems from several issues. There is no federal law requiring people to wear seat belts. Many people feel that this is a state issue rather than a federal issue. Like with so many laws and regulations, there is a resistance to giving the power to the federal government. Therefore, up to this point, it has been up to the states to decide their own laws. The federal government does provide extra funding for states that have greater than the national average for seat belt use, which is its way of encouraging states to make these laws because states pass seat belt laws in order to raise their state seat belt use and to receive the federal grants. According to United States code: Title 23,157, in 2005 states could receive up to $112 million in grants from the federal government if their seat belt use is above the national average.

Also, some people feel that they should be able to choose whether or not to wear a seat belt while in a car. They feel that the government is interfering too much in matters, which they believe are of personal choice.

Some people, especially in older generations, also believe that they are in fact safer in a car without wearing a seat belt. They feel that a seat belt would keep them from being able to get out of the car in the event of an accident or other emergency. Although this is true in instances of submerged vehicles and some fires, in the vast majority of accidents seat belts have been proved to be beneficial in preventing serious injuries. Deaths from automobile accidents have decreased 35% in the past 30 years.

**Seat Belt Safety From a mechanical standpoint seat belts are one of the most important safety features in the automobile. The purpose of the seat belt is to keep passengers inside of the automobile cabin. In physics terms, seat belts aim to keep the sum of the forces (∑F) on the occupants as close to zero as possible by applying a force to the occupants in the opposite direction as the collision. When it comes to analyzing collisions, ∑F plays a key role but the most important quantity in a collision is the automobile’s Change in momentum (∆p) or Impulse (J). Even in low speed automobile collision the car undergoes a very large (∆p). Because of this, seat belts must deliver the same ∆p to the automobile occupants as the collision. It is because of this that seat belts do not necessarily need to deliver a force equal to the force of the collision, they just need to create the same magnitude ∆p, in the opposite direction of course. According to Newton’s second law ∆p is defined as ∫F*dt. So in the event of a collision a seat belt will deliver a force to a passenger over a certain interval of time, this will keep the passenger inside of the car while delivering to them a less that lethal force. ** Most seat belts rely simply on Newton’s third to deploy. Upon impact the collision will deliver some force to the occupants, if the force is too great if will trip a mechanical force sensor, and that sensor will immediately lock the seat belt in place. Once the seat belt has been locked it will delivery a force to the occupant that is equal to the force the occupant applied to it. ** In order for seat belts to apply a high impulse with a not so high force they must have a certain amount of “give” to them, that is they must stretch when a certain force is applied to them. This quantity is described as a modulus. The lower the modulus the more the seat belt will give but if the modulus is too low the seat belt will not provide enough support. Seat belt have a certain modulus designed to maximize their strength while also maximizing the amount stretch. **
 * How Seat Belts Deploy
 * Seat Belt Modulus

**Key Equations to Seat belts**

They key is keeping the ∑F as close to zero as possible to minimize the acceleration of the occupants Change in Momentum and Impulse are dependent on the force applied and the time. Maximizing the time the seat belt applies the force minimizes the magnitude of that force. Newton’s third law. When the occupant pushes on the seat belt the seat belt pushes back with a force equal in magnitude but opposite in direction The modulus of the seat belt is the amount of stress or pressure the seat belt is taking over the amount that it stretches or strain while under that pressure. In this case pressure is directly proportional to the applied force as the area if the seat belt stays the same.

The graph above models the stress vs. strain for a certain unknown material. The modulus can be found by taking the slope of the graph between the origin and the yield stress point. At the point labeled UTS the object reaches a point where is no longer returns to its original length. Seat belts stay in the region before this but they still give a little bit.

Connection
Federal and State governments pass laws regarding seat belt use and manufacturing in order to encourage people to use seat belts. This has led to a 35% drop in accident fatalities in the last 30 years. According to James Madison University, when seat belts are used properly, they reduce serious injuries by 50% and have the potential to reduce the number of fatalities by 60 - 70 %. Clearly, the fact that seat belts reduce the impact of a collision to the human body contributes to these statistics.

Sources for this page:
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