Best Practice

BEST PRACTICE:

G5-6: Work Zone Intrusion Alarms

DESCRIPTION:

Work zone intrusion alarms are impact-activated safety devices that warn work zone personnel of errant vehicles entering a protected work zone area. There are four main types of intrusion alarms: microwave, infrared, pneumatic tubes, and kinematic. Microwave and infrared models are mounted on traffic drums or cones and use microwave signals or beams of infrared light to connect units. When a vehicle crosses into the work zone and interrupts the signal or beams, a high-pitched alarm is sounded near the workers. The pneumatic tube model is placed on the ground, with the tubes laid perpendicular to traffic. When a vehicle drives into the area and over the tubes, the alarm sounds. The kinematic models are mounted on a traffic cone (or other similar hardware) and sound the alarm when a change in the orientation angle of the cone indicates that it has been tipped over. This system assumes an errant vehicle has knocked over the hardware and has entered the work area.

Additional alert mechanics from commercially available products include flashing lights, strobe lights, and personal safety devices. Personal safety devices are meant to be attached to a worker’s clothing. When the alarm has been tripped, these devices can wirelessly notify the worker via vibration and/or through a head set. These devices do not require any electrical power and have been accepted as Federal Highway Administration National Cooperative Highway Research Program Report 350 Category II work zone traffic control devices.

REASON(S) FOR ADOPTING:

The primary motive for the adoption of these alarms is to reduce potential work zone collisions and injuries resulting from errant vehicles.

PRIMARY BENEFIT(S):

Intrusion alarms do not require electrical power to function, allowing faster mobile setups and the audible/visual alarms provide workers additional time so that they can react in order to avoid potential collisions.

MOST APPLICABLE LOCATION(S)/PROJECT(S):

These devices are most applicable in any work zone where sight distance and worker visibility is limited.

STATE(S) WHERE USED:

Iowa, Kansas, Maryland, Minnesota, Montana, Ohio, Oregon, Pennsylvania, Washington

SOURCE/CONTACT(S):

Dan Sprengeler, Traffic Control Engineer, Iowa DOT
Phone: (515) 239-1823
E−mail: Dan.sprengeler@iowadot.us