The Evaluation of the Surrogate Safety Measures Along a Pedestrian Confined Ramp of an Old Bridge
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Summary
This study addresses the challenge of evaluating pedestrian safety in confined, high-density environments where traditional accident data is scarce and unreliable. The authors focus on the Stari Most bridge in Mostar, Bosnia and Herzegovina, a narrow pedestrian ramp with a 20% slope and specific structural features like kerbs. The research aims to assess safety levels and identify critical conflict zones by analyzing pedestrian trajectories and interactions under varying flow conditions, rather than relying on rare accident reports. This approach allows for a proactive assessment of safety risks in tourist-heavy areas where pedestrian mobility is increasing. The methodology involved a four-step process: geometric analysis of the bridge, video surveillance of natural pedestrian behavior, data extraction using a semi-automatic detection and tracking tool (T-Analyst), and subsequent analysis of surrogate safety measures. Video recordings were captured during peak hours in September 2018. The researchers tracked individual trajectories to calculate behavioral parameters (speed, acceleration) and surrogate safety indicators, including Time-To-Collision (TTC), Time Advantage (TAdv), T2, and relative speed (Delta-V). Four scenarios were analyzed, ranging from low density (two pedestrians) to high density (eight pedestrians), with a specific "Beta-tester" (a middle-aged male) tracked across all conditions to observe behavioral consistency. The results revealed distinct patterns in pedestrian behavior and safety risks. In low-density scenarios, flows were balanced between directions, whereas high-density conditions showed a dominant flow direction. Trajectory analysis indicated that pedestrians prefer walking along the longitudinal axis of the bridge, avoiding walls and obstacles. Surrogate safety metrics showed that relative speeds between facing pedestrians averaged 0.81 m/s. Crucially, the analysis of TTC identified the central zone of the ramp as the most critical area, where the majority of near-misses and conflicts occurred. When flows were balanced, conflicts centered in the middle of the ramp; when one direction dominated, conflicts shifted toward the ramp ends. The study confirmed that TAdv values frequently dropped below the 1-second threshold for risky encroachments, particularly in denser scenarios. The significance of this work lies in demonstrating the viability of using surrogate safety measures and video-based trajectory tracking to evaluate pedestrian safety in confined spaces without waiting for accidents to occur. The findings suggest that the central axis of such ramps is the primary conflict zone due to pedestrian path preferences. Consequently, the authors propose that installing a dividing element, such as a short wall or handrail, in the center of the ramp could effectively reduce collisions between opposing flows. This approach provides a replicable framework for assessing and improving safety in similar infrastructures, such as pedestrian bridges, corridors, and sidewalks, by identifying critical zones and testing potential interventions through simulation.
Key finding
The central zone of the pedestrian ramp is the most critical area for conflicts, suggesting that a central dividing element would reduce interactions between opposing flows.
Methodology
field_study
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via author_sweep_intake on 2026-05-28.
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
| 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 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| 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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- Empirical Findings: crash risk outcomes