260930 Estimating the Effect of Individual Components of the Graduated Driver Licensing System on Teen Fatal Crash Involvement

Monday, October 29, 2012 : 11:10 AM - 11:30 AM

Johnathon P. Ehsani, MPH , School of Public Health, University of Michigan Transportation Research Institute, University of Michigan, Ann Arbor, MI
C. Raymond Bingham, PhD , Transportation Research Institute, University of Michigan, Ann Arbor, MI
Jean T. Shope, MSPH, PhD , Transportation Research Institute (Young Driver Behavior and Injury Prevention Group), University of Michigan, Ann Arbor, MI
     
Background

Most studies evaluating the effectiveness of Graduated Driver Licensing (GDL) have focused on the overall system. Studies examining the effect of individual components have rarely accounted for the confounding effect of multiple, simultaneously implemented components. The purpose of this paper is to quantify the effects of four components of GDL (learner license duration, hours of supervised driving, passenger restrictions and nighttime driving restrictions) on teen driver fatal crashes.

Methods

States that introduced a single component, independent of any other component were identified. These represent natural experiments where intervention effects can be potentially measured. Inferences regarding the effect of the single component would be more strongly supported than in situations where multiple GDL components were changed simultaneously. Monthly and quarterly fatal crash rates per 100,000 population of 16- and 17-year-old drivers were analyzed using interrupted time series analysis.

Results

Learner license periods that guarantee a six-month delay in licensure, and twelve-month passenger restrictions were associated with a significant decline in teen drivers' fatal crash rates and fatal passenger crash rates, respectively. There were no significant declines in fatal crashes following the introduction of a required number of supervised driving hours or a nighttime driving restriction.

Discussion

Overall, individual components did not result in the same reductions in crashes observed when multiple components were implemented together. Reductions in teen crashes may be attributed to an extended period of learning and reduced driving exposure with passengers. These findings suggest the need for comprehensive, staged, licensing systems, rather than isolated restrictions and requirements.

Learning Areas:
Public health or related public policy

Learning Objectives:
List the number of levels and components of an optimal Graduated Driver Licensing (GDL) system. Explain why quantifying the contribution of individual components of GDL is challenging. Identify the shortcomings in the existing literature on the effect of GDL. List the components of GDL policies that are associated with a decline in fatal crashes, and those that are not.

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: this is the subject of my doctoral dissertation research.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.

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