Evaluation of California's graduated driver licensing program

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Abstract

Problem: California's graduated driver licensing (GDL) program was implemented to reduce the high crash risk of teenage drivers. The program enhancements made in 1998 were evaluated in this study using methods that rule out the noticeable downward trend in California teen's fatal/injury crash rates as a possible explanation for any observed crash reductions that could otherwise be mistaken for program effects. Method: Monthly per capita fatal/injury crash rates for 15-to-17-year-olds and proportional representations of 16–17-year-olds' nighttime and passenger crashes were analyzed using intervention time series analysis. Results: After removing trend, seasonality, and transition effects in the data, no overall reductions in fatal/injury crashes for 15–17-year-olds or 16-year-olds (separately) were found to be associated with the 1998 program enhancements, suggesting no overall exposure reduction effect of the longer instruction permit period nor increased competency associated with the higher number of required practice hours. However, the 12-month nighttime and 6-month passenger restrictions were found to be associated with annual savings of 55 and 816 fatal/injury crashes, respectively. Discussion: Finding no overall impact of the 1998 GDL enhancements was not surprising given findings of an earlier survey suggesting that California teens and parents were largely already practicing program requirements prior to implementation and were not fully complying with the program requirements afterwards. Though the observed crash savings associated with the restrictions were of modest size, this is the first study to evidence a direct positive impact of the passenger restriction component of GDL programs. Larger reductions could be realized if the nighttime restriction started earlier and parents/law enforcement could be motivated to better enforce these restrictions. Impact on Industry: The findings provide support for passenger and nighttime restriction components of GDL programs.

Section snippets

Problem and purpose

Teenage drivers have a much higher crash risk than do drivers in other age groups because of their fundamental lack of driving skill, inexperience at driving, tendency toward increased risk-taking, immaturity, inaccurate risk perception, and overestimation of driving skills (Janke, Masten, McKenzie, Gebers, & Kelsey, 2003). Licensing authorities have tried to mitigate the increased crash risk of teenagers by implementing modified driver licensing programs for teenagers that focus on improving

Licensing programs for teenagers

Given that research on teen drivers has shown that increased driving experience is associated with reduced crash risk (Ferguson, 1996, Mayhew & Simpson, 1990, Simpson & Mayhew, 1992), many states, provinces, and countries have introduced modified licensing programs for teenage drivers that gradually lift initial licensing restrictions to ease them into higher risk driving situations (Foss & Goodwin, 2003, Mayhew & Simpson, 1984, Mayhew & Simpson, 1996, McKnight, 1996, Shope & Molnar, 2003,

Evaluations of licensing programs for teenagers

States that have adopted even some of the major program components mentioned above have realized lower teenage crash rates (Ferguson et al., 1996, McKnight et al., 1983). Evaluations of GDL programs or their components outside of California have generally found that they are associated with reductions in teen crashes, although there is a lot of variation in the observed effect sizes. The variability may be due to the fact that the programs differ in their components, some being more

California's original (PDL) licensing program for teenagers

To obtain a learner's permit in California, teens younger than age 18 must have completed or be simultaneously enrolled in both driver education and driver training courses or have completed driver education and be enrolled in a driver training course. They also must pass vision and written knowledge tests. The minimum age to apply for an instruction permit changed from 15 years to 15 1/2 years starting January 2004 (subsequent to the completion of this study). To obtain their drivers license

Evaluation of California's PDL program

Hagge and Marsh (1988) evaluated the original California PDL program using time series analysis of statewide crash rates and also an assessment of individual driver records. They found that the program as a whole was associated with 5.3% lower per capita crash rates for 15-to-17-year-olds and 23% lower violation rates for 16-year-old licensed drivers. Compared to the adult program, the accelerated post-licensing control action program for teenagers was found to be superior for reducing

California's enhanced (GDL) licensing program for teenagers

Even though the California PDL program was found to reduce teen crash rates, teenage drivers remained the highest risk age group of California drivers even after the original 1983 program was implemented (Aizenberg & McKenzie, 1997, Romanowicz & Gebers, 1990). In July 1998 the California Legislature enhanced the licensing program for teenagers in response to the recalcitrant high crash risk of teenage drivers in California and the fact that California's PDL program for teenagers did not include

Other evaluations of California's GDL program

Although this study presents some of results from the official California Department of Motor Vehicles' (DMV) evaluation of the enhanced California GDL program, other evaluations of the program have been completed. Results of two evaluations of California's program by the Automobile Club of Southern California suggested that the program was associated with crash reductions (Bloch, 2000, Bloch et al., 2002). Results of another evaluation of the California program sponsored by the California

Methods

Teenage drivers aged 15 to 17 years-old comprised the treatment group for purposes of evaluating the overall impact of the 1998 GDL enhancements, for which adult drivers aged 24 to 55 years-old were used as a control group. All drivers aged 15 to 17 years-old who applied after the program start date were subject to the GDL program requirements during the period in which they held an instruction permit or intermediate drivers license. Age 24 was chosen as the lower bound for the control group

Analyses of the overall impact of GDL

For the following analyses of fatal/injury crashes for 15–17-year-olds and also 16-year-olds, the univariate teen crash series and the multivariate teen crash series, wherein the 24–55-year-old crash series was used to control for variability in the teen series, were all modeled to determine if implementing the GDL enhancements in July 1998 was associated with a gradual-permanent, sudden-temporary, or sudden-permanent change. The univariate fatal/injury crash series for 24–55-year-olds was also

Discussion

This evaluation found that the GDL program enhancements together did not result in a significant overall reduction in teen fatal/injury crashes. However, the nighttime and passenger restrictions were found to be associated with significant reductions in fatal/injury night and passenger crashes, although the reductions were not very large. The California GDL passenger restriction is very stringent, so it is no surprise that this is the first evaluation that the authors are aware of that

Acknowledgements

This study is part of the California Traffic Safety Program and was made possible through the support of the California Office of Traffic Safety, State of California, and the National Highway Traffic Safety Administration. The study was prepared by the Research and Development Branch of the California Department of Motor Vehicles under the administration of Cliff Helander, Chief. The opinions, findings, and conclusions expressed in this study are those of the authors and not necessarily those

Scott Masten is a Research Program Specialist who worked for 7 years with the California Department of Motor Vehicle, Research and Development Branch. He recently started working for the Highway Safety Research Center at the University of North Carolina, Chapel Hill. His primary areas of research are driver education and training, driver testing, and young driver issues. He received BA and MA degrees in psychology from California State University, Sacramento, and is currently pursuing his

References (25)

  • S.A. Bloch

    California teen passenger deaths and injuries drop as graduated driver license law marks second anniversary [News release]

    (2000, September 14)
  • S.A. Bloch et al.

    Does graduated driver licensing reduce drinking and driving? An examination of California's teen driving restrictions

  • Cited by (0)

    Scott Masten is a Research Program Specialist who worked for 7 years with the California Department of Motor Vehicle, Research and Development Branch. He recently started working for the Highway Safety Research Center at the University of North Carolina, Chapel Hill. His primary areas of research are driver education and training, driver testing, and young driver issues. He received BA and MA degrees in psychology from California State University, Sacramento, and is currently pursuing his doctorate in epidemiology at UNC, Chapel Hill.

    Robert Hagge has been a member of California's Department of Motor Vehicles Research and Development Branch since 1982, and for the past 18 years has occupied the position of Research Manager. He has directed or authored numerous research papers on driver competency assessment, licensing, and crash-risk. He is currently managing several research projects, including studies involving the development and evaluation of improved driver competency tests, crash-risk prediction models, and post-licensing driver safety programs. He received his BA and MA degrees in Organizational Communication Studies from California State University, Sacramento.

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