School Start Times and Teenage Driver Motor Vehicle Crashes
archive: archived pipeline: cataloged verified
Get this paper ↗ (full text — opens at the source; we link to it, we don't host it)
Summary
This study investigates whether delaying high school start times reduces motor vehicle crash rates among teenage drivers, motivated by evidence that adolescent sleep deprivation contributes to drowsy driving accidents. Adolescents experience biological shifts in circadian rhythms, requiring later sleep times, yet early school schedules often conflict with these needs. While previous research in Kentucky suggested a crash reduction following a start-time delay, those studies had methodological limitations, including broad age ranges and non-equivalent comparison groups. This research aims to replicate those findings with a more rigorous design, focusing specifically on 16- and 17-year-old drivers during school-in-session periods. The researchers analyzed police-reported crash data from January 2000 through June 2007 in two jurisdictions: Forsyth County, North Carolina, which shifted high school start times from 7:30 am to 8:45 am in August 2003, and Fayette County, Kentucky, which had previously delayed start times. To control for confounding factors, the study included comparison counties in North Carolina (Guilford, Mecklenburg, and Wake) that maintained earlier start times. Monthly time series of crash rates were constructed, adjusted for population changes and excluding non-school days. Intervention time series analysis using ARIMA models was applied to detect downward shifts in crash levels corresponding to the policy changes. In Forsyth County, the analysis revealed a statistically significant decrease in overall crash rates following the start-time delay (one-sided p-value = .04). Hourly breakdowns indicated that crash reductions were most pronounced between 9 am and 3 pm, while crashes increased significantly between 3 pm and 6 pm. This pattern suggests a shift in peak exposure times rather than a reduction in total driving risk, as students left school later. However, no corresponding significant effects were observed in the three North Carolina comparison counties. In Fayette County, Kentucky, the refined analysis found no statistically significant change in crash rates among 16- and 17-year-olds, and anomalous data in the Kentucky comparison county prevented meaningful comparative results. The authors conclude that there is only mild evidence supporting the hypothesis that later school start times reduce teenage driver crashes. The beneficial effect observed in Forsyth County was modest and not replicated in comparable North Carolina counties or in the refined Kentucky analysis. The findings suggest that while delaying start times may shift the timing of crashes to later in the day, it does not necessarily produce a dramatic or consistent reduction in overall crash rates for this age group. The study highlights the need for careful, controlled evaluation of traffic safety policies before widespread adoption.
Key finding
Delaying high school start times resulted in a statistically significant decrease in crash rates among 16- and 17-year-old drivers in Forsyth County, North Carolina, but no significant effect was observed in Fayette County, Kentucky.
Methodology
naturalistic
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 3 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 19 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
Topics
Ranked by relevance to this paper. Hover a topic for its definition.
Information type
What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).
- Empirical Findings: crash risk outcomes