IMPROVED LEFT-TURN SIGNAL OPERATION: HOW THE FLASHING YELLOW ARROW LEFT-TURN DISPLAY CAN ENHANCE INTERSECTION OPERATIONS
Bibliographic record
Abstract
Traffic engineers typically operate under credence the best traffic control is least restrictive. That being said, traffic engineers will deploy, for example, a simple two-phase traffic signal operation before considering multiple complex signal phasing. Two-phase signal control is an efficient way to operate a traffic signal. However, credence is all-so-often challenged as traffic volumes increase such that left-turning motorist experience few available gaps to make a safe maneuver. Traffic engineers are now faced with balancing safety with efficiency. One corresponding mitigation action is incorporation of a protected left-turn phase, which provides a safe maneuver, but green time to serve this protected phase must come from other movements. The resulting increase in safety came at expense of operational efficiency. To regain some of lost efficiency, traffic signals are designed to protect left-turn movement during a portion of signal cycle and allow a permissive movement during remainder of signal cycle, resulting in left-turn control that is commonly known as protected permissive left-turn control, or simply PPLT control (or phasing). If a protected movement is warranted, PPLT control has been shown to increase left-turn capacity and reduce delay at intersections (as compared to protected-only control). Traffic engineers typically determine when to use various left-turn phasing and how to implement chosen left-turn phase treatment after careful consideration of site-specific issues and facts. The National Cooperative Highway Research Program (NCHRP) 3-54 research project has recently completed a comprehensive study on type of display that should be used for permissive left turn movement when used in PPLT control. Findings from NCHRP 3-54 research included recommendation that flashing yellow arrow indication should be included in MUTCD as an alternative to circular green indication for permissive left turn movement when used with PPLT control. This recommendation came as a direct result of studying driver's comprehension and behavioral characteristics along with operational benefits associated with flashing yellow arrow indication. This paper has been prepared to provide an informational overview of some of key elements of NCHRP 3-54 research including: PPLT control and display used within United States, Canada, and Europe; How MUTCD circular green indication is problematic when used for protected permitted left turn operations; Why a comprehensive research study was conducted to identify a display that would reduce safety issues and improve signal operations; Recommendations made in NCHRP 3-54 report, which includes use of flashing yellow arrow display; and. A description of operational advantages of proposed flashing yellow display.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.015 | 0.003 |
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".