Mobile Infrared Transmitter

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A Mobile Infrared Transmitter (MIRT) is an electronic traffic preemption device that city buses and emergency vehicles use to control the traffic control equipment for intersections they are approaching, in order to pass through the intersection as efficiently or safely as possible.


A MIRT device consists of a timer circuit connected to an infrared LED array. The timer causes the infrared LEDs to strobe at specific frequencies, such as 10Hz for low priority (buses) or 14 Hz for high priority (emergency vehicles).[1] Low priority transmitters will control the intersection to perform a normal light change, while high priority transmitters will change an entire intersection immediately.[1][better source needed]

Usage restrictions[edit]

Certain cities use specially encoded infrared pulses to prevent the use of home made transmitters.

The US Government through Congress did plan to make use of MIRT transmitters and other traffic preemption devices a federal offense for unauthorized persons in the United States under the "Safe Intersection Act of 2005". However, this act failed to pass in Congress, and was not enacted. As a result, it is not a federal offense currently[when?] for unauthorized use of MIRTs and other devices used for traffic control preemption.[2]

See also[edit]