An Evaluation of Graduated Driver Licensing Effects on Fatal Crash Involvements of Young Drivers in the United States

Abstract

Objective: Graduated driver licensing (GDL) systems are designed to reduce the high crash risk of young novice drivers. Almost all states in the United States have some form of a 3-phase GDL system with various restrictions in the intermediate phase. Studies of the effects of GDL in various states show significant reductions in fatal crash involvements of 16- and 17-year-old drivers; however, only a few national studies of GDL effects have been published. The objective of this national panel study was to evaluate the effect of GDL laws on the fatal crash involvements of novice drivers while controlling for possible confounding factors not accounted for in prior studies.

Methods: The Fatality Analysis Reporting System (FARS) was used to examine 16- and 17-year-old driver involvement in fatal crashes (where GDL laws are applied) relative to 2 young driver age groups (19–20, 21–25) where GDL would not be expected to have an effect. Dates when various GDL laws were adopted in the states between 1990 and 2007 were coded from a variety of sources. Covariates in the longitudinal panel regression analyses conducted included 4 laws that could have an effect on 16- and 17-year-old drivers: primary enforcement seat belt laws, zero-tolerance (ZT) alcohol laws for drivers younger than age 21, lowering the blood alcohol concentration limit for driving to 0.08, and so-called use and lose laws where drivers aged 20 and younger lose their licenses for underage drinking violations.

Results: The adoption of a GDL law of average strength was associated with a significant decrease in fatal crash involvements of 16- and 17-year-old drivers relative to fatal crash involvements of one of the 2 comparison groups. GDL laws rated as “good” showed stronger relationships to fatal crash reductions, and laws rated as “less than good” showed no reductions in crash involvements relative to the older driver comparison groups.

Conclusions: States that adopt a basic GDL law can expect a decrease of 8 to 14 percent in the proportion of 16- and 17-year-old drivers involved in fatal crashes (relative to 21- to 25-year-old drivers), depending upon their other existing laws that affect novice drivers, such as those used in these analyses. This finding is consistent with recent national studies that used different outcome measures and covariates. The results of this study provide additional support for states to adopt, maintain, and upgrade GDL systems to reduce youthful traffic crash fatalities.

Keywords:

• Graduated driver licensing (GDL)
• Fatality Analysis Reporting System (FARS)
• Drivers aged 16–17
• National panel study
• Regression analyses

ACKNOWLEDGMENTS

This study was funded under grant number 1R21HD056344 from the National Institute of Child Health and Human Development (NICHD). Dr. Michael Spittel was the Federal Project Officer.

The authors extend their appreciation to Dr. Susan Baker, Dr. Li-Hui Chen, and Dr. Guohua Li for their gracious cooperation in providing their GDL database to use for updating and data analyses. We also thank Pedro Torres for his initial data processing services. Finally, a special thanks to Alma Lopez and Stephanie Stevens for their editing and formatting services.

Notes

^a Total for 50 states; state-years with Ns < 10 excluded.

^a Age ratio used for estimate: 16–17/21–25.

^b Calculation performed assuming no change in ratio denominator (16–17/21–25) pre- and post-passage of GDL laws.

^c Calculation performed using actual change in ratio denominator (16–17/21–25) pre- and post-passage of GDL laws.

^d SB = states with primary enforcement seat belt laws; ZT = states with laws for zero tolerance of any alcohol for drivers < 21years in which drivers’ license is forfeited; 0.08 = states with a blood alcohol concentration legal limit of 0.08 g/dL for all drivers; use and lose = states with laws in which persons < 21 years caught with alcohol in any situation lose their driver's license.

^a Three levels of GDL laws were tested: any, good, and less-than-good. GDL laws were rated by the by the IIHS as good, fair, marginal or poor, in descending order. Any refers to all GDL laws regardless of rating. Good refers to only GDL laws rated good. Less-than-good refers to GDL laws in which those rated good were excluded from analysis.

^b SB = states with primary enforcement seat belt laws; ZT = states with laws for zero tolerance of any alcohol for drivers < 21years in which driver's license is forfeited; 0.08 = states with a blood alcohol concentration legal limit of 0.08 g/dL for all drivers; use and lose = states with laws in which persons < 21 years caught with alcohol in any situation forfeit their driver's license.

^a Includes state-years with GDL laws of any IIHS rating and/or no GDL law.

^b SB = states with primary enforcement seat belt laws; ZT = states with laws for zero tolerance of any alcohol for drivers < 21years in which driver's license is forfeited; 0.08 = states with a blood alcohol concentration legal limit of 0.08 g/dL for all drivers; use and lose = states with laws in which persons < 21 years caught with alcohol in any situation lose their driver's license.