Effect of Relative Delay Rate on Predicted Accident at Karbala City Arterial Streets: A Simulation Study

Salah, Majida; Ali Ewadh, Hussein; Rahman Almuhanna, Raid · 2025 · Crossref

DOI: 10.31272/jeasd.2092

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Summary

This study investigates the relationship between the relative delay rate and predicted crash frequencies on urban arterial streets in Karbala, Iraq. The research addresses the challenge of traffic safety evaluation in regions lacking reliable historical accident data, such as Iraq, where local calibration factors for standard safety models are unavailable. By integrating simulation-based delay estimation with predictive safety analysis, the authors aim to quantify how operational inefficiencies, specifically the ratio of experienced delay to acceptable travel time, influence crash likelihood. This approach serves as a surrogate for traditional accident record analysis, which is often unrealistic or incomplete in such contexts. The methodology focuses on Fatima Al-Zahraa Street, a 1.40 km urban arterial featuring three key intersections: Al-Safeena roundabout, Al-Dhareeba, and Sayed Jawda. Traffic volume data were manually collected from video recordings over five days in January 2023, averaging 16 hours per day, to determine peak-hour factors and traffic composition. Free-flow speeds were measured using the moving car method during low-volume periods. These empirical inputs were used to calibrate a microscopic traffic simulation model in PTV VISSIM 2023 (SP 09). The simulation accounted for specific geometric designs and calibrated driver behavior parameters, such as standstill distance and lock-ahead distances, to realistically replicate traffic flow. The model calculated average delays and service levels, which were then used to estimate crash rates via the Highway Safety Manual (HSM). The primary finding establishes a linear relationship between the relative delay rate and the rate of crashes recorded during peak hours. This correlation aligns with previous literature suggesting that higher congestion levels and unstable traffic operations increase crash potential. The study demonstrates that the relative delay rate—a metric derived from simulation outputs—can effectively serve as an operational predictor of safety performance. The results indicate that deteriorating traffic conditions, characterized by increased delay and congestion, directly correlate with elevated safety risks on the studied arterial. The significance of this research lies in its contribution to traffic safety assessment methodologies in data-scarce environments. By validating a combined simulation-prediction framework, the study provides a viable alternative to traditional crash data analysis for Iraqi urban networks. It highlights the utility of PTV VISSIM and the HSM in evaluating the safety impacts of delay mitigation strategies. The findings support the argument that operational metrics like delay can be used to identify safety-critical environments and justify traffic management interventions, thereby improving road safety and traffic efficiency in congested urban corridors.

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

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• incidence prevalence

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• Empirical Findings: crash risk outcomes