Crash rates over time among younger and older drivers in the SHRP 2 naturalistic driving study.

Publication Type
Journal Article
Year of Publication
Simons-Morton, Bruce G; Gershon, Pnina; O'Brien, Fearghal; Gensler, Gary; Klauer, Sheila G; Ehsani, Johnathon P; Zhu, Chunming; Gore-Langton, R E; Dingus, Thomas A
J Safety Res
Start Page
Date Published
2020 06
Accidents, Traffic; Adolescent; Adult; Age Factors; Automobile Driving; Cohort Studies; Female; Humans; Male; Middle Aged; United States; Young Adult

OBJECTIVE: To examine crash rates over time among 16-17-year-old drivers compared to older drivers.

METHODS: Data were from a random sample of 854 of the 3,500 study participants in SHRP 2, a U.S. national, naturalistic driving (instrumented vehicle) study. Crashes/10,000 miles by driver age group, 3-month period, and sex were examined within generalized linear mixed models.

RESULTS: Analyses of individual differences between age cohorts indicated higher incidence rates in the 16-17-year old cohort relative to older age groups each of the first four quarters (except the first quarter compared to 18-20 year old drivers) with incident rate ratios (IRR) ranging from 1.98 to 18.90, and for the full study period compared with drivers 18-20 (IRR = 1.69, CI = 1.00, 2.86), 21 to 25 (IRR = 2.27, CI = 1.31, 3.91), and 35 to 55 (IRR = 4.00, CI = 2.28, 7.03). Within the 16-17-year old cohort no differences were found in rates among males and females and the decline in rates over the 24-month study period was not significant.

CONCLUSIONS: The prolonged period of elevated crash rates suggests the need to enhance novice young driver prevention approaches such as Graduated Driver's Licensing limits, parent restrictions, and post-licensure supervision and monitoring. Practical Applications: Increases are needed in Graduated Driver's Licensing limits, parent restrictions, and postlicensure supervision and monitoring.