Urban Sprawl as a Risk Factor in Motor Vehicle Occupant and Pedestrian Fatalities
DOI: 10.3141/2513-05
archive: archived pipeline: cataloged verified
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Summary
This study investigates the association between urban sprawl and traffic fatalities, addressing the hypothesis that sprawling urban environments contribute significantly to motor vehicle occupant and pedestrian deaths. While traffic crashes are a leading cause of death for Americans aged 1 to 34, previous data linking sprawl explicitly to fatality rates were sparse. The authors define sprawl by characteristics such as low residential density, rigid separation of land uses, lack of distinct activity centers, and poor street accessibility. The research aims to quantify this relationship at the county level to determine if more compact urban forms result in safer traffic outcomes. The researchers conducted an ecological study using data from 448 counties within the 101 most populous metropolitan areas in the United States. They constructed a county-level sprawl index using principal components analysis on six observed variables derived from US Census and Natural Resources Inventory data: three measures of population density (gross, suburban, and urban) and three measures of street accessibility (average block size and proportions of small blocks). This index was transformed to a scale where higher values indicated more compact urban form. The study analyzed the relationship between this index and traffic fatality rates per 100,000 population for 2000, obtained from the Fatality Analysis Reporting System. Regression models controlled for average household size, working-age population proportion, and per capita income. Pedestrian fatality rates were further adjusted for exposure using data on the proportion of work trips taken by walking or public transportation. The results demonstrated a strong, negative correlation between the sprawl index and traffic fatality rates. For every 1% increase in the index (indicating greater compactness), all-mode traffic fatality rates decreased by 1.49% (P < .001). The association was even stronger for pedestrians; after adjusting for pedestrian exposure, pedestrian fatality rates fell by 1.47% to 3.56% for every 1% increase in compactness (P < .001). Counties with the highest sprawl indices (most compact) were located in central areas of major metropolitan regions, while those with the lowest indices (most sprawling) were in outlying areas of smaller metropolitan regions. The model accounted for 47% of the variance in all-mode fatality rates. The study concludes that urban sprawl is a significant risk factor for traffic fatalities, particularly for pedestrians. The findings suggest that compact urban design, which likely encourages lower vehicle speeds and provides better street connectivity, reduces the likelihood of fatal crashes. The authors note that while the study has limitations regarding ecological design and data granularity, the robust results imply that traffic safety should be considered alongside other public health risks associated with sprawl, such as physical inactivity and pollution. Future research should examine these relationships at finer geographic scales and investigate specific street design features, such as vehicle speed limits, to guide countermeasures.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | OpenAlex-citations | — | — | 1 | 2026-06-19 |
| archive | success | semantic_scholar | — | — | 6 | 2026-06-26 |
| extract | success | cached | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-19 |
| chunk | success | chunk | — | — | 1 | 2026-06-19 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-19 |
| promote | success | — | — | — | 1 | 2026-06-19 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-26 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-19 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.
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- Empirical Findings: crash risk outcomes