Real-time control and optimization of traffic signal timing transition for emergency vehicle preemption

Emergency vehicle (EV) operation has a very important role to play in saving lives and reducing property damage. In order to reduce the response time and the impact of EV operation on general traffic, research is underway around the world to find solutions. The EV signal preemption (EVSP) at intersections is one of the most attractive options.; Two control strategies are proposed for EVSP in this thesis. The first one, a real-time control strategy is used for signal transitioning from normal operation to EVSP (transition 1). Its main objective is to ensure that the approaching EV can cross the intersection at operating speed without any time delay, and it is accomplished by determining a suitable distance of EV detection away from the intersection on the basis of the EV operating speed, peak hour traffic conditions, and traffic signal timing plans. Another objective of the real-time control strategy is to decrease the impact of EVSP on general traffic. The impact on general traffic on the EV route is considered when the EV detection distance is determined. The impact on the cross road is considered by dynamically allotting green time that is not required for the EV to the traffic on the cross road according to current traffic conditions at the intersection and the state of signal indications. The real-time control strategy is also enhanced so that it can be used for single intersection control as well as coordinated route control.; The second control strategy, implemented by an optimal control algorithm, is used for the signal transitioning from EVSP back to normal operation (transition 2). Its objective is to decrease the impact of EVSP on general traffic after the EV has cleared the intersection by minimizing traffic queues at the intersection during a shortest possible time. The optimal control theory is first applied to the traffic signal transition problem, and a time-invarying dynamic system is established. A two-phase algorithm, consisting of a relaxation algorithm and a stepwise search strategy, is then adopted to overcome the difficulty in solving the optimal control model, which results from the interrelationship between successive signal sequences.