Coupling Visual Simulation Model (VISSIM) with Surrogate Safety Assessment Model (SSAM) to Evaluate Safety at Signalized Intersections.

Abstract Traffic safety is the main support of transportation engineering. Otherwise, there no benefit to a facility that lacks safety. Despite that, most road engineers in developing countries ignore traffic their designs or adopt traditional methods suffer from data weakness. So an urgent need for surrogate measures more accurate methods. This paper offers assessment at signalized intersections Hilla city’s urban areas using micro-simulation model (VISSM) coupled with Surrogate Safety Assessment Model (SSAM). Three are modeled VISSM (version 10) by calculating flows and speeds extracted field data. Also, geometric characteristics timing signal simulated reach real-world. Then vehicle trajectory files exported SSAM 3). Several indicators conflicts computed SSAM, involving max speeding (Max S), rate deceleration (DR), time post encroachment (PET), collision (TTC). The number, type, severity calculated. categorized into three types according conflict’s angle, rear-end, lane change, crossing conflicts. results showed optimal values two differ one location another, where TTC ranged between (1.5-1.8) s PET (4.7-5.3) s. Rear-end prevailed all sites until reached 55% approaches varied 0.74 as high-risk 1.8 low-risk collision, while (TTCI) 40 St Bab Al Hussein were 0.86 0.82.respectively. Therefore, they both classified intersections. As Al-Mashed intersection (TTCI=1.23), it moderate risk.