Best Practice

BEST PRACTICE:

J1-6: Queue Warning Systems

DESCRIPTION:

Queue Warning Systems are used to warn motorists approaching congested work zones, predictable bottlenecks, or areas with sigh distance limitations of an impending stop or slow down of traffic. Queue Warning Systems typically consist of roadside sensors downstream of Portable Changeable Message Signs (PCMS). When stopped or slowing vehicles are detected by the sensors, warning messages are displayed on the upstream PCMS alerting motorists of the impending traffic conditions.

REASON(S) FOR ADOPTING:

The purpose of implementing Queue Warning Systems is to reduce the number and severity of rear end crashes at these locations.

PRIMARY BENEFIT(S):

Queue Warning Systems can help reduce primary and secondary incidents by alerting drivers to congested conditions. Furthermore, the incident severity is reduced because drivers are prepared for impending congestion. Queue Warning Systems can also help delay the onset of congested conditions. With more uniform speeds, traffic flows more efficiently. This allows higher traffic volumes to pass by the work zone and improves trip travel time reliability. Finally, data collected from the sensors can be used in traffic analyses or after action reviews.

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

Queue Warning Systems are suitable upstream of work zones along frequently congested freeways, facilities with frequent queues in predictable locations, and facilities with sight distance restricted by vertical grades, horizontal curves or poor nighttime illumination.

STATE(S) WHERE USED:

California , Illinois, Michigan, Oregon, Pennsylvania, Texas, Virginia , Washington, Wisconsin

SOURCE/CONTACT(S):

Samir Ead, Construction Safety Coordinator, Caltrans
Phone: (916) 654-4580
E−mail: Samir.ead@dot.ca.gov