Primary enforcement seat belt laws are effective even in the face of rising belt use rates

A recent systematic literature review found that primary enforcement laws are more effective at increasing seat belt use than secondary laws in the United States. This report re-examines the studies included in the systematic review to explore whether the benefits of a primary law differ based on: (1) the baseline seat belt use rate; or (2) whether or not the primary law replaces a secondary law. States that directly enacted primary laws showed larger increases in observed seat belt use (median increase of 33 percentage points). These laws were enacted in the mid-1980s, when baseline belt use rates were below 35%. Smaller, but substantial increases in belt use were observed in states that replaced secondary with primary laws (median increase of 14 percentage points). Baseline belt use rates in these states ranged from 47 to 73%. Primary safety belt laws can further increase seat belt use even in states with relatively high baseline levels of belt use.     

An investigation of state population characteristics that moderate the relationship of state seat belt law and use in the United States

Objectives

Primary enforcement laws have been shown to be effective methods for increasing seat belt use at the state level.

Method

This study investigates state differences in the effectiveness of primary enforcement laws by assessing whether a state's academic achievement, health ranking, economic prosperity, violent crime rates, government effectiveness, gender distribution, or proportion of rural roads moderate the relationship between those laws and seat belt compliance rates.

Results

Aggregate state-level academic achievement, health ranking, government effectiveness, and proportion of rural roads uniquely moderated the seat belt use differences between primary and secondary enforcement states.

Conclusions

This evidence suggests that cultural, social, and demographic differences among regions may be important factors in explaining state-level differences in the effectiveness of primary enforcement of seat belt laws.     

Seat belt use among African Americans,Hispanics, and Whites

OBJECTIVES: This study investigated seat belt use among White, Black, and Hispanic drivers, in cities in which standard enforcement of the belt use law is permitted (primary enforcement) and in cities in which a motorist has to be first cited for another offense (secondary enforcement). Socioeconomic and gender differences in belt use were also studied. METHODS: Belt use observations were obtained at gas stations in Boston, Chicago, Houston, and New York City. In short interviews with drivers, information on race/ethnicity and education was obtained. RESULTS: Belt use was higher in primary enforcement cities, among women, and among those with at least a college degree. In primary law cities there were no clear differences in belt use by race/ethnicity; in secondary cities African Americans were less likely than Whites or Hispanics to be belted, among populations both with and without college degrees. This is consistent with data from other studies indicating that African Americans are more sensitive than Whites to the enforcement of primary laws and are more likely to increase belt use when states shift from secondary to primary. There has been no evidence of enforcement bias against African Americans--increases in citations generally have been greater among Whites than African Americans once primary enforcement is implemented. CONCLUSIONS: More widespread application of primary laws--standard throughout the world but in only 17 US states and the District of Columbia--would increase belt use for all drivers, especially African Americans.     

The use of feedback signs to increase observed daytime seat belt use in two cities in North Carolina

Well publicized enforcement programs in North Carolina have raised seat belt use to about 80%. In an effort to find techniques to raise belt use further, signs providing feedback to drivers on belt use rates were introduced in two communities, Asheboro (population 18,000) and Greensboro (population 183,000). Feedback signs remind motorists about belt use and imply a constant and vigorous enforcement presence. The signs were prominently posted by the roadside at high volume locations; belt use information was changed weekly based on observational surveys. Observed daytime driver belt use in Asheboro increased from an average of 75% before the signs to 89% after the signs were established. At urban sites in Greensboro, driver belt use increased from 80% to 86%. Right front passenger belt use increased significantly in Asheboro but not in Greensboro. There were no changes in belt use at two interstate exit sites in Greensboro. Reasons for the differential success rates may relate to differences in initial belt use rates, community size, amount of publicity, and numbers of encounters with the signs. It is clear, however, that feedback signs can be an important supplement to belt use enforcement programs.     

Predicting seat belt use in fatal motor vehicle crashes from observation surveys of belt use

There is a large difference between the rates of observed seat belt use by the general public and belt use by motor vehicle occupants who are fatally injured in crashes. Seat belt use rates of fatally injured occupants, as reported in the Fatality Analysis Reporting System (FARS), are much lower than the use rates found in observation surveys conducted by the states. A series of mathematical models describing the empirical relationship between FARS and observed rates were explored. The initial model was a 'straw man' and used two simplifying assumptions: (a) belt users and nonusers are equally likely to be involved in 'potentially fatal collisions', and (b) belts are 45% effective in preventing deaths. The model was examined by comparing each state's FARS use rate with the predicted rate. The model did not fit the state data points even when possible biases in the data were controlled. We next examined the assumptions in the model. Changing the seat belt effectiveness parameter provided a reasonable fit, but required an assumption that seat belts are 67% effective in preventing fatalities. The inclusion of a risk coefficient for non-belted occupants also provided a reasonable fit between the model and data. A variable risk model produced the best fit with the data. The major finding was that a model consistent with the data can be obtained by incorporating the assumption that nonusers of seat belts have a higher risk of involvement in potentially fatal collisions than do seat belt users. It was concluded that unbelted occupants are over-represented in fatal collisions for two reasons: (a) because of a greater chance of involvement in potentially fatal collisions in the first place, and (b) because they are not afforded the protection of seat belts when a collision does occur.     

Getting Americans to buckle up: the efficacy of state seat belt laws

Annual state observed safety belt use rates over the period 1991–2001 are examined using time-series cross-section regression analysis. It was found that seat belt laws are associated with higher use rates and that the enforcement provision matters. Primary states experience belt use rates that on average are 9.1 percentage points higher than their secondary counterparts. In addition, the level of the fine imposed by statute has an effect on safety belt use apart from that attributable to the enforcement provision. The current median fine of $25 is associated with an additional 3.8 percentage points increase in belt use. To further increase safety belt use, it is recommended that states adopt primary enforcement and impose fines of at least $50 for violating a seat belt law.     

Method to evaluate the effect of safety belt use by rear seat passengers on the injury severity of front seat occupants

Although the effectiveness of seat belts for reducing injury to rear seat passengers in traffic accidents has been well documented, the ratio of rear-seat passengers restrained by seatbelts remains lower than that of drivers or passengers in front seats. If passengers in rear seats do not wear seat belts, they may sustain unexpected injury to themselves when involved in accidents, and also endanger front occupants (drivers or front seat passengers). This paper focuses on the tendency of front seat occupants to sustain severer injuries due to forward movement of passengers in rear seats at the moment of frontal collisions, and evaluates the effectiveness of rear passengers' wearing seat belts in reducing injuries of front seat occupants. Since the occurrence of occupant injuries depends considerably on the crash severity, we proposed to use pseudo-delta V in regression analysis to represent velocity change during a collision when analyzing statistical accident data. As the crash severity can be estimated from pseudo-delta V, it becomes possible to make appropriate estimations even when the crash severity differs in data. The binary model derived from the ordered response model was used to evaluate the influence on the injury level based on pseudo-delta V, belted or unbelted status, gender and age. Occupants in cars with a hood in the case of car-to-car frontal collisions were extracted from the statistical data on accidents in Japan. Among 81,817 cars, where at least one passenger was present, a total of 6847 cars in which all passengers sustained injuries and which had at least one rear seat passenger aboard were analyzed. The number of killed or seriously injured drivers is estimated to decrease by around 25% if rear seat occupants come to wear seat belts. Also, the number of killed or seriously injured passengers in front seats is estimated to decrease by 28% if unbelted rear seat occupants come to wear seat belts. Thus, wearing of seat belts by previously unbelted rear seat passengers is considered effective in reducing not only injuries to the rear seat passengers themselves but also injuries to front seat occupants.     

Comparison of reporting of seat belt use by police and crash investigators: variation in agreement by injury severity

Purpose: To evaluate agreement between police and trained investigators regarding seat belt use by crash victims, according to injury severity. Methods: We used data from the National Accident Sampling System Crashworthiness Data System (CDS) for front seat occupants, 16 years and older, in crashes during 1993–2000. Crashworthiness Data System investigators determined belt use from vehicle inspection, interviews, and medical record information; their assessment was considered the gold standard for this analysis. Occupant severity of injury was categorized in five levels from no injuries to death. We estimated the sensitivity, specificity, and area under receiver operating characteristic curves for police reports of belt use. Results: Among 48,858 occupants, sensitivity of a police report that a belt was used was 95.8% overall and varied only modestly by injury severity. Specificity of a police report that a belt was not used was 69.1% overall; it was the lowest among the uninjured (53.2%) and greatest among the dead (90.4%). The area under the curve was 0.82 (95% confidence interval 0.82–0.83) overall; this was lowest among those not injured (0.75, 95% confidence interval 0.74–0.76) and increased with injury severity to 0.91 (95% confidence interval 0.90–0.93) among those who died. Conclusion: Police usually classify belted crash victims as belted, regardless of injury severity. But they often classify unbelted survivors as belted when they were not. This misclassification may result in exaggerated estimates of seat belt effectiveness in some studies.     

Sustainability of the effects of the demerit points system on seat belt use: a region-wide before-and-after observational study in Italy

To assess the short and long term effects of the demerit points system on seat belt use, we set a region-wide cross-sectional observational study 3 months before, and 3 and 15 months after the introduction of the scheme (July 2003) in the Veneto Region, Italy. We analysed differences in seat belt use by year of observation, gender and position in the vehicle, and obtained adjusted prevalence ratio (APR) through Poisson regression. A total of 29,303 drivers, 28,778 front and 12,186 rear passengers were observed. Prevalence levels of 54% for drivers and 53% for front passengers in 2003 switched to 83 and 76%, respectively, 3 months after the new legislation, with further slight increases 15 months thereafter. Seventy-four percent rear passengers were still not compliant with the legislation in 2005. The probability of being belted was 25% lower in males than females (APR=0.75, 95% CI 0.73-0.77) at the beginning of the study period. However, the effect of the new legislation was 19% greater among males (APR=1.19, 95% CI 1.16-1.23). A substantial increase in seat belt use was reached and sustained with the demerit points system. Specific efforts should target rear passengers whose seat belt use still remains worryingly low.     

Mathematical models assuming selective recruitment fitted to data for driver mortality and seat belt use in Japan

Previous research has indicated that unbelted drivers are at higher risk of involvement in fatal crashes than belted drivers, suggesting selective recruitment that high-risk drivers are unlikely to become belt users. However, how the risk of involvement in fatal crashes among unbelted drivers varies according to the level of seat belt use among general drivers has yet to be clearly quantified. We, therefore, developed mathematical models describing the risk of fatal crashes in relation to seat belt use among the general public, and explored how these models fitted to changes in driver mortality and changes in observed seat belt use using Japanese data. Mortality data between 1979 and 1994 were obtained from vital statistics, and mortality data in the daytime and nighttime between 1980 and 2001 and belt use data between 1979 and 2001 were obtained from the National Police Agency. Regardless of the data set analyzed, exponential models, assuming that high-risk drivers would gradually become belt users in order of increasing risk as seat belt use among general motorists reached high levels, showed the best fit. Our models provide an insight into behavioral changes among high-risk drivers and support the selective recruitment hypothesis.     

Using naturalistic driving data to identify variables associated with infrequent,occasional, and consistent seat belt use

Seat belt use is one of the most effective countermeasures to reduce traffic fatalities and injuries. The success of efforts to increase use is measured by road side observations and self-report questionnaires. These methods have shortcomings, with the former requiring a binary point estimate and the latter being subjective. The 100-car naturalistic driving study presented a unique opportunity to study seat belt use in that seat belt status was known for every trip each driver made during a 12-month period. Drivers were grouped into infrequent, occasional, or consistent seat belt users based on the frequency of belt use. Analyses were then completed to assess if these groups differed on several measures including personality, demographics, self-reported driving style variables as well as measures from the 100-car study instrumentation suite (average trip speed, trips per day). In addition, detailed analyses of the occasional belt user group were completed to identify factors that were predictive of occasional belt users wearing their belts. The analyses indicated that consistent seat belt users took fewer trips per day, and that increased average trip speed was associated with increased belt use among occasional belt users. The results of this project may help focus messaging efforts to convert occasional and inconsistent seat belt users to consistent users.     

Traffic safety and the switch to a primary seat belt law: the California experience

This study explores whether the change of an existing seat belt law from secondary to primary enforcement enhances traffic safety. In particular, we examine traffic fatalities and injuries in California from 1988 to 1997. During the first half of this period, California law provided for secondary enforcement of its mandatory seat belt law, but in 1993 it upgraded the law to primary enforcement. Controlling for the number of motor vehicle collisions, a Box–Tiao intervention analysis of the time series is used to compare the monthly fatalities and injuries before and after the change in the enforcement provision. The results show that California experienced an improvement in traffic safety in terms of a significant reduction in injuries, but the change in enforcement provision had no statistically significant impact on fatalities.     

Statistical adjustment for misclassification of seat belt and alcohol use in the analysis of motor vehicle accident data

The use of seat belts and alcohol is often mis-reported in police motor vehicle accident reports for a number of reasons. To avoid penalties, occupants often over report seat belt use and under report alcohol use. Police officers sometimes fail to account for evidence such as presence of belt burn, condition of belts, odor of alcohol, crash patterns, etc. Biased conclusions result when using misclassified accident data to estimate the effectiveness of seat belts in preventing injuries and reducing medical costs. We investigated the effects of misclassification of seat belt and alcohol use on the odds ratio of injury as well as medical costs. A statistical method and a SAS program were developed to adjust odds ratios of injury and medical cost estimates to account for misclassification of seat belts and alcohol use. The method allowed for incorporation of variables that could affect misclassification of seat belt and alcohol use. We conducted a Monte Carlo simulation and found that when there were large differences between the misclassification rates for major and minor injury, the unadjusted odds ratio could have up to a 90% bias while our adjusted odds ratio was effectively unbiased. To illustrate the method, we estimated the misclassification rates of seat belt and alcohol use by comparing merged police and hospital reports from Nebraska motor vehicle accident data sets (1996-1997) and then evaluated the bias of the odds ratio of injury and medical costs estimates due to misclassification. Our results showed that the bias of the odds ratio of injury and medical costs due to misclassification of seat belts and alcohol use depended both on the amount of misclassification and the reported frequencies. Misclassification about seat belt and alcohol use only slightly biased the unadjusted odds ratio estimates and mean hospital charge, while misclassification resulted in approximately a 69% underestimate of the total medical costs savings due to seatbelts. However, due to the small size of the merged Nebraska police and hospital data set used to estimate misclassification rates, these results are likely somewhat imprecise.     

Impact of safety belt use on road accident injury and injury type in Kuwait

The enactment of Kuwait's seat belt law in January 1994 provided an opportunity to examine the impact of seat belt use on road accident fatalities and injury types in this affluent Persian Gulf nation. Via a structured data form, the results of injurious/fatal road accidents for more than 1200 accident victims were gathered from the files of the six major government hospitals which treat most traffic accident victims. Statistical analysis of the data showed that seat belt use has had a positive effect in reducing both road traffic fatalities and multiple injuries in Kuwait. The use of seat belts has also affected the nature of the injuries resulting from road traffic accidents. Non-users of belts experienced higher frequencies of head, face, abdominal and limb injuries. Users of belts, on the other hand, suffered higher frequencies of neck and chest injuries. The interrelationship between the victim, his age, and the type of injuries resulting from road traffic accidents is also investigated.     

Personal,temporal and spatial characteristics of seriously injured crash-involved seat belt non-users in Hawaii

The characteristics of crash-involved seat belt non-users in a high use state (Hawaii) are examined in order to better design enforcement and education programs. Using police crash report data over a 10-year period (1986-1995), we compare belted and unbelted drivers and front seat occupants, who were seriously injured in crashes, in terms of personal (age, gender, alcohol involvement, etc.) and crash characteristics (time, location, roadway factors, etc.). A logistic regression model combined with the spline method is used to analyze and categorize the salient differences between users and non-users. We find that unbelted occupants are more likely to be male, younger, unlicensed, intoxicated and driving pickup trucks versus other vehicles. Moreover, non-users are more likely than users to be involved in speed-related crashes in rural areas during the nighttime. Passengers are 70 times more likely to be unbelted if the driver is also unbelted than passengers of vehicles with belted drivers. While our general findings are similar to other seat belt studies, the contribution of this paper is in terms of a deeper understanding of the relative importance of various factors associated with non-use among seriously injured occupants as well as demonstrating a powerful methodology for analyzing safety problems entailing the categorization of various groups. While the former has implication for seat belt enforcement and education programs, the latter is relevant to a host of other research questions.     

Availability, functionality, and use of seat belts in Beijing taxis prior to the 2008 Beijing Olympic Games

Use of driver seat belts and availability and functionality of passenger seat belts in a convenience sample of 231 Beijing taxis were examined in the months prior to the 2008 Beijing Olympic Games. Driver and front passenger seat belt use was mandated in China from 2004 to help address the growing public health crisis of road trauma. Results from observations made by in-vehicle passengers revealed that 21.2% of drivers were correctly wearing a belt, approximately half were not, and one third were using the belt in a non-functional way. Over 3/4 of this sample of taxi drivers were unrestrained while working. The percentage of functionally available belts was higher for front than rear passengers (88.3% and 22.9%, respectively). This low rate of belt availability in rear seats calls into question the preparedness of the fleet to cater for the safety needs of foreign visitors to China, particularly those from countries with high levels of restraint use. Factors influencing the use/misuse of seat belts in China remain largely unexplored. Results of this pilot study support further investigations of barriers to using injury prevention mechanisms such as seat belts in less motorised countries.     

Evaluation of the Boost ‘em in the Back Seat Program: Using fear and efficacy to increase booster seat use

Objectives

Recent research supports the use of high-threat messages when they are targeted appropriately and designed to promote high efficacy as well as fear. This research examined the effectiveness of using a novel threat-appeal approach to encourage parents to place their children in booster seats and rear seats of vehicles.

Method

A 6-min video-intervention was created and evaluated at after-school/daycare centers via an interrupted time series design with similar control sites for comparison. Caregivers (N = 226) completed knowledge and practice surveys and fear and efficacy estimations related to childhood motor vehicle hazards. Researchers observed booster-seat and rear-seat use in study site parking lots.

Results

Compared to baseline and control assessments, the treatment groups’ child passenger safety knowledge, risk-reduction attitudes, behavioral intentions, sense of fear related to the hazard, and sense of efficacy related to the recommended behaviors increased significantly. Further, observed overall restraint use and booster-seat use increased significantly following the intervention.

Conclusions

Applying high-threat messages to child passenger safety interventions is promising and has the potential to be adapted to other health risk areas.     

A numerical investigation into the effect of CRS misuse on the injury potential of children in frontal and side impact crashes

This research focuses on an investigation into the head and neck injuries sustained by toddlers due to CRS misuse under frontal and side impact crashes. A fully deformable FE model incorporating a Hybrid III 3-year-old dummy was developed which has been previously validated for frontal impacts under CMVSS 208 and FMVSS 213 testing conditions. Furthermore, this model has also been validated under near-side impact conditions in accordance to crash tests carried out by NHTSA. In addition, numerical models incorporating a Q3/Q3s prototype child crash test dummies were developed. The objective of this research was to study the effect of seatbelt slack and the absence of the top tether strap on the head and neck injuries sustained by toddlers in a vehicle crash. Numerical simulations were conducted under full frontal and near side impact crash testing conditions in accordance with FMVSS 213 for the Hybrid III 3-year-old dummy and Q3/Q3s dummies in the absence and presence of slack in the seatbelt webbing, and in the absence and presence of the top tether strap. In addition, the effect of using a cross-shaped rigid ISOFIX system was also investigated. An analysis of the head and chest accelerations, neck loads and moments was completed to investigate the potential of injury due to CRS misuse. An increase in HIC₁₅ by approximately 30–40% for the frontal impact and 10–20% for the near-side impact respectively was observed for the Q3 child dummy due to both forms of CRS misuse. In the absence of the top tether strap the forward head excursions were observed to be increased by approximately 70% for the Hybrid III 3-year-old dummy and 40% for the Q3 dummy, respectively. Use of the cross-shaped rigid ISOFIX system illustrated a reduction in head and neck injury parameters, for both frontal and side impact conditions, in the absence and presence of CRS misuse. CRS misuse results in a significant increase in injury parameters and potential for contact related head injuries. Use of a rigid ISOFIX system to restrain a CRS provides better CRS and dummy confinement and reduced injury potential than a flexible ISOFIX system.