Assessing the Impact of Increasing Tractor-Trailer Speed Limit on the Safety and Mobility of Three-Lane Highways in Egypt

Currently, the speed limit for tractor-trailers (TTs) on Egyptian highways is 30 km/h lower than passenger cars (PCs). The main purpose of this article therefore to evaluate effects an increase in TT both traffic safety and mobility three-lane highways, with limits 90 100 PCs. A SUMO simulation model was used analysis. Average vehicle delay as a measure mobility, while simulated conflict ratio based time collision (TTC) deceleration rate required avoid crash (DRAC) surrogate measures were performance indicators safety. All vehicles equipped measurement (SSM) devices extract conflicts, TTC ≤ 2.50 representing less sever conflicts; 1.50 s DRAC ≥ 3.35 m/s2 potential 0.50 6.0 severe conflicts. results show that increasing TTs would significantly reduce average by approximately 27–76% volumes 500–2000 vehicle/hr/lane, comprising 2.5–15% total volume. Furthermore, most cases, when comparing situation after base case (i.e., 60 70 PCs), no statistically significant change more 1.0, suggesting there change. due TTs, some cases different thresholds, reduction ratio, indicating improvements terms