Spoofing An Emergency Traffic Preemption Signal

A researcher reverse-engineered the Tomar Strobecom II Emergency Vehicle Preemption (EVP) system, which uses infrared light signals to turn traffic lights green for approaching emergency vehicles. By purchasing real hardware, they analyzed the infrared protocol and found that Opticom systems encode data by skipping pulses, while Strobecom systems modulate pulse length. Using an Arduino Nano and an IR LED, they successfully triggered the preemption signal and transmitted a valid vehicle ID. The research shows these systems require precisely timed signals and, in some cases, a valid vehicle ID — making casual spoofing non-trivial, and any real-world attempt legally risky.