What is the difference between Low Priority and High Priority preemption?
Low Priority is generally used by mass transit authorities to increase the time duration of green lights or and/or decrease the time duration of cross-traffic red lights. High Priority takes precedence over Low Priority, and the purpose is to secure control of the intersection by maintaining a single direction of traffic flow by holding the traffic signal green until the emergency vehicle has passed through that intersection. Low Priority is generally considered to be 10 hertz (10 flashes-per-second) while High Priority is 14 hertz. The MIRT is only available in HIGH PRIORITY 14 hertz.
