Simulation Results Suggested That the Knowledge of Detailed Trajectory Information Could Save Approximately 3,000 Lives Annually in the United States by Reducing Critical Response Times.
US Simulation Study Explored the Benefits of a Novel Emergency Vehicle Preemption System.
Nationwide, United States
Informed Traffic Signal Preemption for Emergency Vehicles
Summary Information
Delays caused by red lights can significantly hinder the timely response of emergency vehicles (EMVs). While some cities in developed countries have implemented EMV preemption systems using acoustic, optical, radio frequency, or GPS technologies, their broader deployment remains limited due to high costs and complex maintenance requirements. These systems also tend to experience interference from weather conditions and physical obstructions. To address these challenges, this study proposed a new preemption approach that utilizes predicted trajectory data and real-time traffic conditions to proactively control signals ahead of EMVs. The system integrates safe driving considerations and signal phase change policies with built-in safety buffers to ensure reliability. Its effectiveness was evaluated through a detailed discrete event simulation.
Methodology
The proposed EMV preemption system includes two core components: (1) obtaining the roadway map and predicting the EMV’s trajectory, and (2) scheduling safe and timely transitions of red signals to green along the vehicle’s route. To evaluate its effectiveness, the system underwent two phases of testing. In the first phase, performance was compared across five benchmark maps. The second phase involved running simulations on each of the five maps using five different EMV starting times, with identical departure times applied across all maps for consistency. In both phases, results from the proposed system were compared to a control scenario where red lights remained unchanged. A standard five-second delay was applied whenever an EMV encountered a red light.
FINDINGS
- With signal preemption, EMV travel speed increased by one percent, resulting in average time savings of 66 seconds in simulation map five and 39 seconds across all five simulation maps.
- The preemption system reduced the average proportion of red traffic signals in the simulated trips by around 58-75 percent.
- Based on the improvements demonstrated in the simulations, the time savings gained through trajectory awareness and communication with traffic signals could potentially save around 3,000 lives annually out of the 356,000 out-of-hospital cardiac arrests that occur each year in the United States.
- The proposed preemption system may also help reduce stress for first responders by making it easier and safer to pass through intersections, especially when approaching during a red light.
