Enhancing safety and efficiency of signal intersections: A part-time protected right-turn signal control for straight-right lane in connected environment

Straight-right lanes (SRL) are commonly used to improve efficiency of intersections considering urban land dimensions. However, straight-through vehicles (STV) could block right-turn vehicles (RTV) crossing the intersection during the red phase on SRL, resulting in not only low efficiency but also more rear-end conflicts. The advent of connected environments enables urban intersections to collect a large variety of data concerning arriving vehicles and provides an opportunity for real time optimization of signal control plans. This technic could be effectively used to dispose the above dilemma. To this end, the present study proposes a part-time protected right-turn signal control (PPRSC) for SRL to enhance safety and efficiency at intersections. A dynamic queue length (DQL) mechanism is proposed to guide PPRSC. This mechanism is dynamically updated at cycle level using an ant colony optimization (ACO) algorithm which takes expected traffic conflicts and potential waiting time into account. The introduced strategy is tested on a field intersection modeled through the cellular automata (CA) model simulation. Results indicate a decrease in expected traffic conflicts of SRL by 15.3 % and speed fluctuation decreased by 10.88 % for RTV. Besides, average speed of RTV increases by 25.5 %, accompanied by a 60.8 % and 65.7 % reduction in traffic delay and average waiting time, respectively. The findings delineate that the developed PPRSC has great potential to enhance both potential safety and efficiency benefits at signalized intersections.