To stop, or not to stop, that it the dilemma: evaluating the effects of safety countermeasures at signalized intersections during the yellow phase

Calvi, Alessandro; D'Amico, Fabrizio; Ferrante, Chiara; Petrella, Claudio · 2022 · Crossref

DOI: 10.54941/ahfe1002480

archive: archived pipeline: cataloged verified

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Summary

This study addresses the safety challenges posed by the "dilemma zone" at signalized intersections, where drivers hesitate between stopping or proceeding as the traffic light turns yellow. This indecision leads to inconsistent behaviors, increasing the risk of red-light violations, right-angle collisions, and rear-end crashes. The research aims to evaluate the effectiveness of three specific safety countermeasures in resolving this dilemma and improving driver decision-making. The researchers conducted a driving simulator experiment using a validated fixed-base simulator at Roma Tre University. The scenario involved a two-lane urban road with a 50 km/h speed limit and five signalized intersections. Forty-six participants drove the scenario under four conditions: a baseline with no countermeasures, and three interventions. Countermeasure C1 was a Green Signal Countdown Timer (GSCT) displaying remaining green seconds. Countermeasure C2 consisted of horizontal pavement markings and vertical "STOP/GO" signs placed at the stopping sight distance. Countermeasure C3 was an in-vehicle advanced driving assistance system using augmented reality and connected vehicle technology to provide personalized "STOP" warnings based on the driver’s actual speed and distance. Data collected included stop/go decisions, red-light running (RLR) rates, and speed profiles. The results indicated that Countermeasure C3 was the most effective, significantly reducing both the length of the dilemma zone and the rate of red-light running to 1.2%, compared to 4.9% in the baseline condition. Countermeasure C2 also performed well, achieving the largest reduction in the dilemma zone length (31% shorter than baseline) and promoting the most consistent driver behavior. Conversely, Countermeasure C1 proved ineffective and detrimental to efficiency; it expanded the dilemma zone to 41.1 meters and caused an unnecessary increase in early stopping rates. Drivers using the countdown timer began decelerating earlier, leading to stops even when they could have safely crossed the intersection, thereby reducing intersection functionality. The study concludes that personalized, speed-based in-vehicle warnings (C3) offer the highest safety benefits by minimizing wrong decisions and red-light violations. Pavement markings and signs (C2) are also effective for standardizing driver behavior. However, green signal countdown timers (C1) are discouraged as they increase hesitation and reduce traffic flow efficiency. These findings suggest that future intersection safety strategies should prioritize connected vehicle technologies and standardized visual cues over simple countdown displays.

Key finding

An augmented reality in-vehicle assistance system was the most effective countermeasure for reducing red light running and the dilemma zone length, while countdown timers increased unnecessary early stopping and reduced intersection efficiency.

Methodology

simulator

Sample size: 46

Provenance

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Topics

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• rail grade crossings
• perceptual countermeasures