Assessing the Impact of Safety Countermeasures on Dilemma Zones at Signalized Intersections of Urban Roads: a Driving Simulator Study
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Summary
This study investigates the "dilemma zone" (DZ) at signalized urban intersections, a critical safety issue where drivers hesitate whether to stop or proceed when the traffic light turns yellow. This indecision leads to inconsistent behaviors, increasing the risk of rear-end collisions and right-angle crashes. The research aims to identify effective countermeasures to resolve the DZ, thereby improving intersection safety and efficiency. The authors tested three specific interventions: Green Signal Countdown Timers (GSCT), a new scheme of vertical warning signs and horizontal pavement markings, and an in-vehicle advanced driving assistance system using Augmented Reality (AR) and connected vehicle technologies. The experimental design utilized a fixed-based, medium-fidelity driving simulator featuring a modified Toyota Auris and a 180-degree curved screen. Forty-six participants drove a simulated four-kilometer urban road scenario with a 50 km/h speed limit. The scenario included five signalized intersections where the light turned yellow at varying distances to the stop line (28m, 42m, 56m, 69m, and 83m). Each participant completed four drives: one baseline condition with no countermeasures and three experimental conditions, each implementing one of the tested countermeasures. The GSCT displayed a countdown of the remaining green seconds; the sign/marking scheme provided a static "STOP/GO" cue based on stopping sight distance; and the AR system provided personalized, real-time "STOP" warnings based on the driver’s actual speed and distance. The results indicated that the GSCT (C1) was ineffective, increasing the DZ length to 41.1 meters compared to the baseline of 29.2 meters. This countermeasure also generated an "option zone" that led to inconsistent driver decisions and a higher rate of unnecessary stops, reducing intersection efficiency. In contrast, the sign/marking scheme (C2) and the AR system (C3) significantly reduced the DZ length by 30.5% and 21.6%, respectively. C2 demonstrated the greatest consistency in driver decision-making, while C3 recorded the fewest wrong behaviors (only 3 instances compared to 9 in the baseline and 12 in C2). The AR system successfully provided timely warnings tailored to individual driving conditions, whereas the static signs relied on assumed speed limits. The study concludes that vertical/horizontal warning signs and AR-based in-vehicle systems are effective tools for mitigating dilemma zones and enhancing safety at urban signalized intersections. These measures reduce driver indecision and improve the homogeneity of stop/go decisions. Conversely, green signal countdown timers may exacerbate safety risks by encouraging inconsistent behaviors and premature stopping. The findings suggest that future implementations should prioritize personalized, real-time warning systems or clear static cues over simple countdown timers to optimize intersection operations and reduce crash potential.
Key finding
Warning signs and augmented reality-based in-vehicle systems effectively reduced the dilemma zone length and improved driver decision consistency, whereas green signal countdown timers increased the dilemma zone and led to more inconsistent behaviors.
Methodology
simulator
Sample size: 46
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-05 |
| archive | success | canonical_url | — | — | 1 | 2026-06-06 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
| clean | success | clean | — | — | 1 | 2026-06-07 |
| chunk | success | chunk | — | — | 1 | 2026-06-07 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-07 |
| promote | success | — | — | — | 1 | 2026-06-05 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Applied Guidance: countermeasure evaluation