Safety Evaluation of Permanent Raised Snow-Plowable Pavement Markers
Bibliographic record
Abstract
Permanent raised pavement markers (PRPMs) often are used to improve preview distances and guidance for drivers in inclement weather and low light conditions. However, studies in three states in the United States have raised concerns about these devices after negative safety effects were found. To address these concerns, an NCHRP project was initiated to assess definitively the safety effects of PRPMs and to develop guidelines for their implementation, by using state-of-the-art methodology and a database from across the United States. This project evaluated the safety performance of snow-plowable PRPMs on two-lane roadways and four-lane freeways by using data collected from five states. The results show that on two-lane roadways selective installations in one state were accompanied by highly significant decreases in total, nighttime, and wet-weather crashes, whereas there was no apparent overall safety benefit for the nonselective installations in two states. A disaggregate analysis of those results found that the nighttime crash effects can be larger on higher-volume roadways and those with degree of curvature of 3.5 or less (radius larger than 500 m). On four-lane freeways, there were some positive indications for wet-weather, guidance-related, and nighttime crashes, with the effects for nighttime crashes increasing as traffic volumes increased. The results of the disaggregate analysis were used to recommend Manual on Uniform Traffic Control Devices guidelines for the implementation of PRPMs.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.012 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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 teacher head, 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".