Work Zone Intrusion Alarms: A Short Course on What They Are and Why They Are Needed

This article discusses the need for intrusion alarms to warn highway workers of moving vehicle intrusion into work zones. The original alarm system developed under the Strategic Highway Research Program (SHRP) used ultrasonic and infrared beam technology. Since the development of this system, manufacturers have also adopted microwave, pressure activated (pneumatic tube), and laser technologies. These various technologies are described. Intrusion alarm systems usually include a detection/transmitter unit and a receiving unit with a siren which sounds upon interruption of the trigger source. Some systems also include strobe lights and radar detection activation to warn oncoming drivers. Alarm system setup, basically the same regardless of technology used, is described. Results of field evaluations in Washington State and New York State are included.