Analyzing the Effects of Geometric and Traffic Parameters on Critical Conflicts Using the Time-to-Collision (TTC) Safety Index at Urban Signalized Intersections

Document Type : Original Article

Authors
kamran sarvari 1
Aminmirza Boroujerdian 2
1 M‌.Sc., Grad., Faculty of Civil and Environmental Engineering, Tarbiat Modares, University, Tehran, Iran
2 Associate Professor, Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran.
10.22034/road.2025.522889.2396
Abstract
Road transport safety is a key component of sustainable urban development, playing a crucial role in reducing accidents and human casualties. With rapid urbanization and increasing traffic volumes, attention to factors influencing traffic accidents has grown significantly. Thus, the scientific analysis of traffic behavior and identification of safety-related factors—especially at critical points like urban intersections—is essential for effective traffic planning and management. Signalized intersections are widely used in urban traffic systems due to their benefits in controlling flow and enhancing safety. They are considered key, sensitive elements in urban traffic networks, primarily designed to reduce conflicts among road users and improve flow in congested areas.This study analyzes the safety of urban signalized four-way intersections using the Time-to-Collision (TTC) index. Field data was collected through aerial imagery with drones at seven high-traffic intersections in Saqqez city. Traffic and geometric variables such as traffic volume, speed, and entry width were extracted and analyzed using the Data From Sky software and image processing algorithms. Multiple linear regression models revealed that for every additional vehicle in traffic volume, the number of critical TTC conflicts increases by approximately 1.2%. Furthermore, an increase of one meter in the entry width of each intersection can reduce the number of critical collisions based on the TTC index by 24% to 28%.
Keywords
Safety Four-Leg Signalized Intersections
Time to collision
Performance Analysis
Image Processing
Traffic Conflicts
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