Utilizing Partial Least-Squares Path Modeling to Analyze Crash Risk Contributing Factors for Shanghai Urban Expressway System
Bibliographic record
Abstract
Currently, frequent crash occurrences significantly influence traffic operation conditions and travel reliability for urban expressway systems. Therefore, it is vital to understand the crash occurrence mechanisms and then introduce safety improvement countermeasures. Emerging studies have been conducted to unveil the relationships between traffic operation conditions and crash occurrence with advanced traffic-sensing data. However, the majority of previous studies have only identified correlation relationships, which are insufficient for traffic-safety improvement. On the other hand, existing crash causal investigations have limitations of utilizing aggregated traffic-flow data and considering the crash occurrence mechanisms only in a reflective way (in contrast to the formative way). In this study, the confounding impacts among crash risk contributing factors and the crash causal relationships were revealed through the partial least-squares path modeling (PLS-PM) analysis approach. Data from the Shanghai urban expressway system in China were utilized for the empirical analyses. First, random forest models were adopted to rank the variable importance, and a total of six contributing factors were selected as inputs that feed into the PLS path models. Then, two different causal relationship structures (formative and reflective) were established, and the best-fitted model structures were identified. The results showed that average operation speed has negative impacts on crash occurrence, and the variables indicated that disturbed traffic flows have positive causal relationships. Finally, the analysis results shed some light on proactive safety management strategies.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".