Increasing seat belt usage in the United States has proved to be a slow and difficult task.

It has taken about 30 years since the National Highway Transportation Safety Administration (NHTSA) conducted the first seat belt and child restraint workshops in 1978 to reach 84 percent usage in 2009. In general, seat belt laws and their enforcement have received the greatest emphasis since 1984. 

There has been less emphasis on increasing fine amounts as a means to increase usage, in spite of positive circumstantial and research evidence.

To remedy this, Bedford Research and the Pacific Institute for Research and Evaluation conducted a study for NHTSA to determine the relative impact of primary seat belt laws and fine amounts on seat belt usage. The research examined changes in usage associated with past activities and estimated gains that might be expected in the future.

Conducting the study

The study determined the impact of various predictors on two measures of seat belt use. The first was the percentage of buckled front-seat occupants over age eight killed in passenger vehicles, as found in NHTSA's Fatality Analysis Reporting System (FARS), which is a census of all crashes involving fatalities in the United States. Because seat belt use among the fatally injured is consistently measured, FARS use is a reliable estimate of belt use.

The second measure was the percentage of front-seat occupants of passenger vehicles observed to be buckled up in annual statewide observational surveys conducted by each state in accordance with criteria established by NHTSA.

Penalties for violations

Based on information obtained from the states, penalty amounts (fines plus fees and court costs) have increased over the past decade. The sum of these charges averaged $35 in 2000 and $49 in 2008. Twenty-six states increased their total penalty by at least $5. In these states, the average penalty increased from $39 to $70. FARS use increased by an average of about 9.1 percentage points.

In the remaining 24 states, there was a small decline (on average) in total fine-and-fee amount, from $30 in 2000 to $26 in 2008. FARS use increased by six points in these 24 states -- about two-thirds the gain experienced by the 26 states that increased their total fine plus fee assessments.

High-belt-use states versus low-belt-use states

States were ranked by their two most recent years of observed seat belt use (2007-2008) and placed into three groups based on these rankings. They were: "Top 10,” "Bottom 10,” and a "Middle” group of 30 states plus the District of Columbia.

Nine of the 10 states with the highest use had primary seatbelt laws; nearly half of the middle group had such laws; and only three of the 10 states with the lowest use had primary laws. New Hampshire, among the 10 states with the lowest use, has no adult seat belt law.

Impact of law type

There were two time periods examined in the study: 1997-2002 -- a period of Operation Always Buckle Children (ABC) mobilizations -- and 2003-2008 -- a period of Click It or Ticket (CIOT) enforcement mobilizations.

Primary seat belt laws (versus secondary laws) had the most consistent impact on seat belt usage across the two time periods. Primary laws accounted for 10- to 12-percentage-point increases in seat belt usage among occupants observed during daytime hours (observed use) and 9-point increases among occupants killed in crashes (FARS use).

Higher fines were associated with higher seat belt use, particularly in the most recent time period (2003-2008). The results showed that increasing the fine amount from $5 to $25 had approximately the same effect as changing the fine from $25 to $60; both were associated with three- to four-point increases in usage in primary or secondary law states.

A fine increase of $60 to $100 was associated with gains of two to three percentage points in belt use. Little improvement was associated with fines above $100, but there were few states with fines above this level.

Enforcement, as reported during the two weeks of the mobilizations each year, was related to higher FARS and observed seat belt use. These measures, however, were deemed too unreliable to estimate potential gains in annual seat belt use because of reporting limitations.

Media expenditures as reported during the two CIOT weeks were not associated with increases in usage after accounting for variations associated with laws, fines, and enforcement. Some low-use states focused on media more than actual enforcement.

Effect on the odds of seat belt use

The analysis also examined the change in the odds of seat belt use associated with each predictor. The odds ratio is a measure of the odds of being buckled up in any given year, divided by the odds of being buckled in the baseline year. This measure is more sensitive to relative change for states that already have high use rates.

Primary laws (versus secondary laws) were associated with 7.9 to 26.2 percent increases in the odds of belt use. A fine increase from the median $25 to $100 was associated with 11.3 to 29.6 percent increases in belt use.


The analyses confirmed that primary seat belt laws and fine increases were associated with higher use rates and with increases in the odds of being buckled.

Fine amounts were consistently associated with seat belt use across the two time periods and for both FARS and observed belt use. An increase in fine level from $25 (the current median value in both primary and secondary law states) to $60 was associated with a three- to four-percentage-point increase in both FARS and observed seat belt use. Increasing a state's fine level from $25 to $100 was associated with a 6- to 7-point increase in both use rates.

An upgrade from secondary to primary enforcement was associated with a 10- to 12-percentage-point increases in observed use and 9-point increases in FARS use. This increase is additive to the increase associated with a fine increase.

In summary, the study found that increasing fine levels is a strategy that has potential to further raise seat belt use, in addition to primary law upgrades and high-visibility enforcement.

Although the analyses did not find a statistically significant effect associated with media, experts believe the public needs to be aware of laws and fine changes before compliance is likely. "Publicizing fine increases is essential for maximizing their effectiveness," they conclude.