Intersection Sight Distance Requirements for Basic Turbo Roundabouts
Bibliographic record
Abstract
Turbo roundabouts, emerging as a solution to conventional multilane roundabouts’ safety and operations concerns, are prevalent in Europe and are still new to North America. However, few studies and guidelines on intersection sight distance (ISD) requirements exist. This paper focuses on the basic turbo roundabouts, examines the circulatory roadway and approach design features, and develops ISD models with North American practices. The ISD requirements were identified for the vehicle approaching and entering the roundabout, which conflicts with the circulating vehicle in the circulatory roadways, and the entering vehicle at the upstream entry approach. Analytical models were developed to identify the required lateral clearance at the central island and clear sight triangles at the roundabout quadrants to satisfy the required ISD. The analyses were completed for four typical sizes of basic turbo roundabouts per Dutch design criteria. The design guidelines are provided for the required lateral clearance at the central island and the required clear sight triangles at the roundabout quadrants. They would be beneficial in establishing landscaping restrictions and determining the roadway right of way and property impacts at the intersections during the roadway planning stage.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".