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.
Description
A MIRT device consists of a
timer circuit connected to an
infrared LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
array. The timer causes the infrared LEDs to
strobe
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek ('), meaning ...
at specific frequencies, such as 10
Hz for low priority (buses) or 14 Hz for high priority (emergency vehicles). Low priority transmitters will control the intersection to perform a normal light change, while high priority transmitters will change an entire intersection immediately.
Usage restrictions
Certain cities use specially encoded infrared pulses to prevent the use of home made transmitters.
People buying and selling the devices hit a roadblock in August 2005 when
President George W. Bush passed the
Safe, Accountable, Flexible, Efficient Transportation Equity Act.
It established a minimum sentence of six months in prison for anyone who uses the device illegally. The act also said those selling the device illegally could serve a year in prison, according to the U.S. Department of Transportation Web site.
See also
*
Traffic signal preemption
References
Road safety
External links
"Hackers target traffic lights" at TMCnet{{Road