Comparison of crash rates and rear-end striking crashes among novice teens and experienced adults using the SHRP2 Naturalistic Driving Study

ABSTRACT

Objective: Motor vehicle crashes are the leading cause of death for teens. Previous teen and adult crash rates have been based upon fatal crashes, police-reported crashes, and estimated miles driven. Large-scale naturalistic driving studies offer the opportunity to compute crash rates using a reliable methodology to capture crashes and driving exposure. The Strategic Highway Research Program 2 (SHRP2) Naturalistic Driving Study contains extensive real-world data on teen and adult driving. This article presents findings on the crash rates of novice teen and experienced adult drivers in naturalistic crashes.

Methods: A subset from the SHRP2 database consisting of 539 crash events for novice teens (16–19 years, n = 549) and experienced adults (35–54 years, n = 591) was used. Onboard instrumentation such as scene cameras, accelerometers, and Global Positioning System logged time series data at 10 Hz. Scene videos were reviewed for all events to identify rear-end striking crashes. Dynamic variables such as acceleration and velocity were analyzed for rear-end striking events. Number of crashes, crash rates, rear-end striking crash severity, and rear-end striking impact velocity were compared between novice teens and experienced adults.

Results: Video review of the SHRP2 crashes identified significantly more crashes (P < 0.01) and rear-end striking crashes (P < 0.01) among the teen group than among the adult group. This yielded crash rates of 30.0 crashes per million miles driven for novice teens compared to 5.3 crashes per million miles driven for experienced adults. The crash rate ratio for teens vs. adults was 5.7. The rear-end striking crash rate was 13.5 and 1.8 per million miles driven for novice teens and experienced adults, respectively. The rear-end striking crash rate ratio for teens vs. adults was 7.5. The rear-end striking crash severity measured by the accelerometers was greater (P < 0.05) for the teen group (1.8 ± 0.9 g; median = 1.6 g) than for the adult group (1.1 ± 0.4 g; median = 1.0 g), suggesting that teen crashes tend to be more serious than adult crashes. Increased rear-end striking impact velocity (P < 0.01) was also observed for novice teens (18.8 ± 13.2 mph; median = 18.9 mph) compared to experienced adults (3.3 ± 1.2 mph; median = 2.8 mph).

Conclusion: To our knowledge, this is the first study to compare crash rates between teens and adults using a large-scale naturalistic driving database. Unlike previous crash rates, the reported rates reliably control for crash type and driving exposure. These results conform to previous findings that novice teens exhibit increased crash rates compared to experienced adults.

KEYWORDS:

• Naturalistic driving
• SHRP2
• novice teens
• crash rate
• rear-end striking
• crash severity

Acknowledgments

The authors thank David McDonnell from the Department of Electrical Engineering at Drexel University for his contribution to the analysis. The authors are grateful to Dr. Flaura Winston, Dr. Kristy Arbogast, and Ayana Bradshaw for investing resources from the Center for Injury Research and Prevention (CIRP) to develop naturalistic driving studies and analytical techniques. The authors also acknowledge the staff at the Virginia Tech Institute of Technology who answered numerous technical questions to facilitate the development of a data sharing agreement and data transfer; especially Miguel Perez and Suzie Lee. The authors also thank Daniel Loeb, mathematician, for his help with the statistical analysis.

Funding

The authors acknowledge the National Science Foundation (NSF) Center for Child Injury Prevention Studies IU/CRC at the Children's Hospital of Philadelphia (CHOP) and the Ohio State University (OSU) for sponsoring this study and its Industry Advisory Board (IAB) members for their support, valuable input, and advice. This material is also based upon work supported by the National Science Foundation under Grant Number EEC-1062166. The views presented here are solely those of the authors and not necessarily the views of CHOP, CIRP, OSU, the NSF, or the IAB members.