National Automotive Sampling System (NASS) General Estimates System (GES) : analytical user's manual, 1988-1997
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Summary
This document serves as the analytical user’s manual for the National Automotive Sampling System (NASS) General Estimates System (GES), covering data collected between 1988 and 1997. Published by the National Highway Traffic Safety Administration (NHTSA), the manual addresses the need for reliable data to support highway safety programs, regulatory initiatives, and cost-benefit analyses. The GES was designed to provide a nationally representative probability sample of police-reported motor vehicle crashes, focusing on incidents involving fatalities, injuries, or major property damage, thereby concentrating on crashes of greatest concern to public safety. The methodology involves a complex three-stage sampling design. First, Primary Sampling Units (PSUs), defined as cities, counties, or groups of counties, are selected from 1,195 units across the United States, categorized by geographic region and urbanization type. Second, police jurisdictions within these PSUs are sampled with probability proportional to the number of crashes investigated. Third, Police Accident Reports (PARs) are selected from these jurisdictions, stratified into four groups based on vehicle type, injury status, and towing requirements. Data collectors visit approximately 400 police agencies across 60 sites to obtain copies of selected PARs, which are then coded into electronic files by trained personnel. In 1997, approximately 55,000 PARs were sampled and coded. To handle missing data, the system employs univariate imputation, which assigns values based on known proportions, and hot-deck imputation, which uses correlated variables to estimate unknown values. The resulting data are organized into three SAS data sets: the Accident File, containing environmental and roadway characteristics; the Vehicle/Driver File, detailing vehicle attributes and driver behaviors; and the Person File, recording information on all individuals involved, including injury severity and demographics. The manual provides comprehensive definitions for hundreds of variables, noting changes made throughout the 1988–1997 period. It also explains how to calculate national estimates using the provided case weight variable, which accounts for the inverse probabilities of selection at each sampling stage. The document includes guidance on interpreting imputed variables, identified by specific suffixes, and offers examples of SAS programs for analyzing the data. The significance of the GES lies in its ability to generate statistically valid national estimates of crash characteristics, including probable errors. By restricting the sample to police-reported crashes, the system provides a consistent basis for identifying safety problems and evaluating interventions. The manual ensures that researchers, government agencies, and industry stakeholders can accurately interpret and utilize the data, facilitating evidence-based decision-making in highway safety. The inclusion of detailed variable definitions and imputation procedures enhances the transparency and reliability of the analyses conducted using this dataset.
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| 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 |
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| enrich | success | — | — | — | 1 | 2026-05-23 |
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| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 48 | 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.
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- Empirical Findings: crash risk outcomes
- Methodological Resource: dataset resource