Effect of New Jersey's GDL Decal Law on Young Probationary Drivers’ Crashes and Citations

Abstract

Background: Decal laws have been implemented internationally to facilitate police enforcement of Graduated Driver Licensing (GDL) restrictions (e.g., passenger limit, nighttime curfew), but have not been evaluated. New Jersey (NJ) implemented the first-in-the-U.S. decal law on 5/1/10.

Purpose: Evaluate the effect of NJ’s law on the rate of citations issued for violation of GDL restrictions and police-reported crashes among probationary drivers <21 years old and estimate the number of probationary drivers whose crashes were prevented by the law.

Methods: NJ’s licensing and crash databases were linked from 1/1/08-5/31/11 and each driver’s license status, age, and outcome status were ascertained for each month. Monthly rates were calculated as the proportion of probationary drivers who experienced the outcome in that month. The pre-law period was defined as 1/08-1/10 and the post-law period as 5/10-5/11. Negative binomial regression models with robust standard errors were used to determine the law’s effect on crash and citation rates (adjusted for gender, seasonal trends, and overall trends) and estimate prevented crashes. Analyses were conducted in 2012.

Results: In the first year post-law, there was a 14% increase in the GDL citation rate (adjusted RR [95% CI]: 1.14 [1.05, 1.24]), a 9% reduction in the police-reported crash rate (aRR [95% CI]: 0.91 [0.86, 0.97]), and an estimated 1,624 young probationary drivers whose crashes were prevented.

Conclusion: Findings suggest the law is positively impacting 66 probationary drivers’ safety. Results provide valuable information to U.S. and international policymakers considering decal laws to enhance their GDL laws and contribute to building the evidence base for decal laws.