Primary Enforcement of Mandatory Seat Belt Laws and Motor Vehicle Crash Deaths.
BACKGROUND
Policies that allow directly citing motorists for seat belt non-use (primary enforcement) have been shown to reduce motor vehicle crash deaths relative to secondary enforcement, but the evidence base is dated and does not account for recent improvements in vehicle designs and road safety. The purpose of this study was to test whether recent upgrades to primary enforcement still reduce motor vehicle crash deaths.


METHODS
In 2016, researchers used motor vehicle crash death data from the Fatal Analysis Reporting System for 2000-2014 and calculated rates using both person- and exposure-based denominators. Researchers used a difference-in-differences design to estimate the effect of primary enforcement on death rates, and estimated negative binomial regression models, controlling for age, substance use involvement, ﬁxed state characteristics, secular trends, state median household income, and other state-level trafﬁc safety policies.


RESULTS
Models adjusted only for crash characteristics and state-level covariates models showed a protective effect of primary enforcement (rate ratio, 0.88, 95% CI=0.77, 0.98; rate difference, -1.47 deaths per 100,000 population, 95% CI= -2.75, -0.19). After adjustment for ﬁxed state characteristics and secular trends, there was no evidence of an effect of upgrading from secondary to primary enforcement in the whole population (rate ratio, 0.98, 95% CI=0.92, 1.04; rate difference, -0.22, 95% CI= -0.90, 0.46) or for any age group.


CONCLUSIONS
Upgrading to primary enforcement no longer appears protective for motor vehicle crash death rates.
Department of Epidemiology, Biostatistics and Occupational Health, The Institute for Health and Social Policy, and the Department of Economics, McGill University, Montreal, Canada. Electronic address: sam.harper@mcgill.ca.
Sam
S
Harper
Department of Epidemiology, Biostatistics and Occupational Health, The Institute for Health and Social Policy, and the Department of Economics, McGill University, Montreal, Canada.
Erin C
EC
Strumpf
D000063:Accidents, Traffic / Q000401:mortality* / Q000517:prevention & control*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001336:Automobiles / Q000331:legislation & jurisprudence* / Q000706:statistics & numerical data; D002648:Child; D006801:Humans; D035846:Law Enforcement / Q000379:methods*; D008875:Middle Aged; D015233:Models, Statistical; D012622:Seat Belts / Q000331:legislation & jurisprudence* / Q000706:statistics & numerical data; D011049:Social Control Policies; D013597:Systems Analysis; D014481:United States / Q000453:epidemiology; D055815:Young Adult