University of Wisconsin, Madison
About the research
Back-of-queue crashes are a significant safety hazard in highway work zones—especially those with intermittent congestion. A number of intelligent transportation systems (ITS) have been developed to provide queue warning, but historically the cost and complexity of these systems have limited their use.
The objective of this project was to design a low-cost queue warning system (QWS) to reduce costs, simplify deployment, and test in the field. The developed low-cost QWS could allow back-of-queue warning signs to be installed wherever queuing is anticipated (even for short-term projects). Modular design of the low-cost QWS will allow the system to be extended as far upstream as necessary to provide ample driver notification in high-, medium-, and low-demand situations.
The sign support system for a low-cost QWS went through several iterations of design in order to find a design that has been crash tested and approved to the Manual for Assessing Safety Hardware (MASH) standards. The final design of the sign support system is based on a non-proprietary support system crash tested by the Texas A&M Transportation Institute. The proposed sign support design for the low-cost QWS has not been able to be field tested for several reasons. The most notable reason is highway agencies are strongly encouraged for safety and liability reasons to only use hardware systems that have successfully completed crash-testing protocols in accordance to the safety standards in the MASH. To date, only a select few sign support systems have been crash tested to MASH criteria, and none with the type of low-cost QWS hardware required for this prototype.
The second reason was the inability to find field test sites on conventional two-lane highways with 55 mph speed limits and the requirement that the equipment be located outside of a clear zone or shielded by protective barriers. Expressway and freeway facilities can’t be used for testing for this design because the Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD) requires larger size signs and font letter sizes for the message required on these types of facilities. Therefore, before field testing can be undertaken on highways open to traffic, an investment in funding for crash testing is strongly recommended.