Document Type : Research Paper
Authors
Civil Engineering Department, University of Babylon, Babylon, Iraq.
Abstract
In situations where reliable crash data is unavailable, Surrogate Safety Measures (SSMs) become valuable tools for traffic safety research. This study focuses on assessing traffic safety at signalized intersections, specifically examining how traffic operations such as stopped delay time and Level of Service affect hourly traffic conflicts using surrogate measures. Three four-leg signalized junctions in Karbala City were selected. Data on traffic volume and conflicts were collected using video cameras managed by the Karbala Traffic Police. The VISSIM software was utilized for traffic operation analysis, which then served as input for the Surrogate Safety Assessment Model (SSAM) software. The results show that simulation-based hourly traffic conflicts increase as stopped delay time increases, with a correlation coefficient between them ranging from R2 = (0.9127-0.7533). Specifically, stopped delay values ranged from 117 seconds at the Sayed Jawda intersection (considered high-risk) to 79 seconds at the Al-Sofaraa intersection (considered low-risk). Rear-end conflicts accounted for the highest percentage of total conflicts, reaching 63%, 58%, and 66% at the respective intersections. This high percentage is attributed to rear-end conflicts predominantly occurring within the same approach in the traffic queue. This research provides valuable insights into evaluating safety at signalized intersections in urban areas and serves as an additional reference for future road safety studies. This study differs from previous research by emphasizing the correlation between stopped delay time and the frequency of hourly traffic conflicts using SSAM software. This study provides a more nuanced understanding of the relationship between operational characteristics and safety at signalized intersections.
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