Crash Risk of Cell Phone Use While Driving: Case-Crossover Study of SHRP 2 Naturalistic Driving Data

Owens, Justin M.; Tefft, Brian C.; Guo, Feng; Fang, Youjia; Pérez, Miguel A.; McClafferty, Julie; Dingus, Thomas A. · 2018 · openalex

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Summary

This study investigates the relationship between cell phone use and crash risk using data from the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study. Motivated by ongoing debate regarding the extent to which smartphones impair driving safety, the research aims to quantify crash risk associated with specific cell phone tasks while controlling for driver-specific and situational factors. Unlike previous studies that relied on simulators, near-crashes, or less controlled observational data, this analysis focuses exclusively on real-world crashes and employs a rigorous case-crossover design to isolate the impact of distraction. The researchers analyzed data from 3,593 drivers monitored via in-vehicle video and sensors between 2010 and 2013. The study utilized a case-crossover design, comparing cell phone use in the six seconds immediately preceding a crash to the same driver’s behavior during up to four matched baseline epochs of ordinary driving. These baselines were selected from within three months prior to the crash and matched for time of day, weather, locality, lighting, speed, and traffic density. The final sample included 566 severe, moderate, and minor crashes matched to 1,749 baseline segments. Conditional logistic regression was used to estimate odds ratios (ORs) for various cell phone activities, including conversation, texting, dialing, browsing, and reaching for the phone, relative to driving without secondary tasks. The results indicate that visual-manual cell phone tasks significantly increase crash risk. Overall visual-manual interaction was associated with an OR of 1.83 (95% CI: 1.03–3.25), while texting specifically yielded an OR of 2.22 (95% CI: 1.07–4.63). Risk was further elevated in free-flow traffic conditions (OR 2.46) and for specific crash types where the driver played a clear role, particularly rear-end crashes (OR 7.77) and run-off-road crashes (OR 3.15). In contrast, hand-held cell phone conversation showed a slight, non-significant increase in risk (OR 1.16, 95% CI: 0.50–2.70). Hands-free conversation could not be meaningfully assessed due to insufficient data. The study concludes that visual-manual interactions, particularly texting, are significant risk factors for crash involvement, whereas conversational tasks do not show a statistically significant association with crashes in this controlled analysis. The estimated risks were lower than those found in previous studies, likely due to the strict matching of baseline epochs, which inherently controlled for individual driver characteristics and environmental variables. These findings provide robust evidence for traffic safety advocates and policymakers, highlighting the specific dangers of visual-manual distraction while driving and suggesting that regulations or interventions should prioritize mitigating these high-risk behaviors.

Key finding

Visual-manual cell phone tasks, particularly texting, significantly increased the odds of crash involvement compared to driving without secondary tasks, whereas hand-held conversation did not show a statistically significant increase in risk.

Methodology

naturalistic

Sample size: 3593

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StageOutcomeToolModelPromptAttemptsCompleted
discover success 1 2026-05-28
archive success canonical_url 4 2026-06-06
extract success cached 3 2026-06-10
clean success clean 1 2026-06-07
chunk success chunk 1 2026-06-07
embed success embed Qwen/Qwen3-Embedding-8B 1 2026-06-07
enrich skipped 4 2026-07-02
promote success 1 2026-06-04
summarize success llm qwen3.6-27b-prismaquant summ-v5 2 2026-06-10
tag success vector_similarity 15 2026-06-11
verify success 2 2026-06-10

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