Transportation Deployment Casebook/2014/Safety Belt Policy Implementation

Qualitative AnalysisEdit

Mode DescriptionEdit

With the invention of cars, safety measures needed to be implemented to ensure a positive view of the automobile. Large metal vehicles traveling at high speeds can be very unsafe in the event of a car crash. There are two common types of safety restraints for automobiles. The first is a two-point system, which goes across the driver or passengers lap. This restrains the driver/rider from harmful movement in the event of a collision or sudden stop. The second, safer, type of safety belt is the three-point belt. It not only goes across the driver’s waist, but across the chest as well. Connecting one shoulder to one hip. This spreads that energy across the body.

The SceneEdit

The automobile was made popular in the 1990s. With the invention of the car by Karl Benz in 1886.[1] The automobile did not become popular until the early 1900s when the Ford Company created the Model T. The Ford Company was able to rapidly produce cars for growing demand.

Demand was not the only thing growing. Speeds of automobiles were also increasing. Road accidents are the largest lead cause of death worldwide. With increasing speeds and technologies with the car, safety improvements needed to be made.


The safety belt was invented in 1773 by Sir George Cayley, the pioneer of flight, and was used as rudimentary harnesses on aircrafts.[2] The early automobiles were equipped with this two-point design until Volvo invented the tree-point safety belt. The three-point belt was invented in 1959, and by 1963 they were commonly fitted for the driver.[3] Seatbelt studies have been found to reduce fatality rates in car crashes by 50-70%.[4]

Early Market DevelopmentEdit

It was believed upon the invention of the seatbelt that seatbelts would increase risky driving behavior. This is called the compensation theory. It was believed that introducing the seatbelt would make drivers feel safer driving a faster speeds and would not consider how their actions would affect other drivers and pedestrians and bikers.[5] The invention of the safety belt was cautioned in early times to eliminate this unsafe driving behavior.

The Role of Policy in Birthing PhaseEdit

In 1997, the federal government set a goal of increasing seat belt usage from 68% in 1996 to 85% by 2000. This first goal was not achieved. The second part of their goal was to increase the seatbelt usage all the way to 90% by 2005. This goal was also not reached. Currently, in 2014, the seatbelt usage rate is at 87%,[6] still under the federal goal.

The federal government encouraged states to adapt new laws within their boundaries to encourage safety belt usage to reach this national goal. The first state to adapt a seatbelt regulation was New York State in 1984. All but one state, New Hampshire, have adopted seat belt use laws.[7]

Two types of laws were implemented by states to increases usage. The first type is Plain Law. Police are able to award tickets to drivers that are caught not wearing their seatbelt when pulled over for other causes. This law has been found to increase seatbelt usage be 11 percentage point.[8] The second type of enforcement is ‘primary enforcement’. This gives the police the ability to pull drivers over solely for the reason of an unbuckled seatbelt. This type of regulation increases safety belt use by 22 percentage points.[9]

The Growth of the ModeEdit

States began implementing safety belt regulations in 1984. The last state to implement a law was in 1995. Since then no other states have been adding laws (New Hampshire being the only state without a safety belt law). 1986 was the highest number states creating laws enforcing seat belt use with 14 states adding laws. By this year, two years after New York made the first law, nearly half of the states had police enforcements of safety belt use. By the following year 1987, 29 states had laws.

States creating primary enforcement laws grew less quickly. New York was again the first state with primary enforcement. New York's initial regulation implemented in 1984 was primary enforcement. With the most states upgrading to primary enforcement being in 2006 and 2009 with four states adding primary enforcement measures. Currently, in 2014, only 34 states have primary enforcement.

Development during the Mature PhaseEdit

The mature phase occurs when 90 percent of the states are enforcing seatbelt laws. This occurred in 1993. States were rapidly instituting laws requiring seatbelt laws. The highest number of states occurred only two years after the mature phase started with 7 more states adding laws. The number of states with laws has hit a plateau since 1995 with New Hampshire being the only states that has not created a law. (See charts below).[10]

Lock-in and ReinventionEdit

Whenever a new law is put into place, the amount of people that use seatbelts increases greatly right after the law is put into effect. The use of seatbelts then decreases with time.[11] This makes it impossible to get to 100% seatbelt use.

Recently, cars have instituted chimes on the dashboard that alert the driver when they themselves are unbuckled, or their passengers. This new technology has the possibility of increasing the number of seat belts used in newer vehicles.

Drivers also now have the opportunity to reduce the cost of their insurance by having cameras installed in their cars that monitor their safe driving habits. These cameras can see if drivers and passengers are using their seatbelts. If the driver practices this safe habit, they can have their car insurance reduced. Instituting this requirement in more vehicles will increase the safety belt usage percentage. Hopefully, this percentage will get to the federal goal of 90%, and eventually 100%.

Quantitative AnalysisEdit

Data CollectionEdit

Data was collected from the Insurance Institute for Highway Safety.[12] This site compiles a list of states that have enforcement laws and primary enforcement laws for seat belt use.


Safety Belt Implementation
Seatbelt Laws by State
Seatbelt Primary Enforcement Laws by State
Seatbelt Laws and Primary Enforcement by State

Data was regressed using the year as the independent variable, and number of states with laws as the dependent variable.


Y=LN(number of states with law/(K-number of states with law))

K = 51. The highest possible number of states with laws. (50 states plus Washington D.C.)

For states with any law enforcement

b (slope)=0.518



For states with primary enforcement

b (slope)=0.12


R-squared= 0.95

Curve FittingEdit

Once the regression was completed, the values were plugged into the following formula and added to the graphs of state data points.

The equation: S(t)=K/(1+EXP(-b(t-t0)))


With laws around the world being put into place to increase traffic safety, the federal government left it to the states to create laws increasing seatbelt use. By 1995, all of the states that currently have seatbelt laws had their laws set in place. With more and more safety concerns, states required primary enforcement. Throughout the growth phase, more and more states added laws, but at a slower rate than general safety belt laws. The maturity phase was reached much faster with general safety belt laws and is still in effect with the primary enforcement. Using the curvilinear line of best fit, the model predicts that by the year 2035 all states will have laws, and by the year 2044 all states will have primary enforcement. These predictions are just ‘best guesses’ but show how long the maturity phase will be for seat belt law implementation


  1. Georgano, G.N. (1985), “Cars: Early and Vintage, 1886-1930. London: Grange-Universal.
  2. Manby, F. (2009), “Clunk, Click – An Invention That’s Saved Lives for 50 Years,” Yorkshire Post. Retrieved Oct. 31st, 2014.
  3. Manby, F. (2009), “Clunk, Click – An Invention That’s Saved Lives for 50 Years,” Yorkshire Post. Retrieved Oct. 31st, 2014.
  4. Levitt, S.D., and Porter, J. (1999), “Sample Selection in the Estimation of Air Bags and Seat Belt Effectiveness,” NBER Working Paper 7210.
  5. Cohen, A., and Einav, L. (2001), “The Effects of Mandatory Seat Belt Laws on Driving Behavior and Traffic Fatalities,” Discussion Paper 341.
  6. “Seat Belt Use in 2013 – Use Rates in the States and Territories”. DOT HS 812 030: A Brief Statistical Summary. National Highway Traffic Safety Administration. May 2014.
  7. Cohen, A., and Einav, L. (2001), “The Effects of Mandatory Seat Belt Laws on Driving Behavior and Traffic Fatalities,” Discussion Paper 341.
  8. Cohen, A., and Einav, L. (2001), “The Effects of Mandatory Seat Belt Laws on Driving Behavior and Traffic Fatalities,” Discussion Paper 341.
  9. Cohen, A., and Einav, L. (2001), “The Effects of Mandatory Seat Belt Laws on Driving Behavior and Traffic Fatalities,” Discussion Paper 341.
  10. "Safety Belt and Child Restraint Laws"". Insurance Institute for Highway Safety. November 2013.. Retrieved 2013-11-01. 
  11. Williams, A.F., Lund, A.K., Preusser, D.F., and Blomberg, R.D. (1987), “Results of a Seat Belt Use Law Enforcement and Publicity Campaign in Elmira, New York,” Accident Analysis & Prevention 19(4): 243-249.
  12. "Safety Belt and Child Restraint Laws". Insurance Institute for Highway Safety. November 2013.