Evaluation of the Effectiveness of a Variable Advisory Speed System on Queue Mitigation in Work Zones

Variable Advisory Speed Systems (VASS) provide drivers with advanced warning regarding traffic speeds downstream to help them make better decisions. Vehicle use on highways is increasing and the need to improve highways brings increased construction of highways, which increases the need for reducing the number of traffic lanes thus reducing capacity during construction. This often causes queues at the entrance to work zones. The purpose of this study was to evaluate the effectiveness of a VASS at mitigating queues in work zone entrances. It was anticipated that by implementing a VASS that queues would be reduced and vehicle flow increased in work zone areas. Three objectives of this study are: (1) research VASS systems that can be tested, (2) select and deploy a VASS in Utah at a long-term work zone, (3) perform a statistical analysis on traffic flow characteristic data to evaluate the effectiveness of the VASS that was deployed. A literature review on use of VASS for work zones showed minimal research had been done on VASSs. A VASS was selected and the work zone for the study was selected as the I-15 Beck Street Widening Project. The VASS consisted of five sensors and two variable message signs (VMS’s). To determine if the system was effective at reducing queue the speed data were analyzed to come to statistical conclusions. It was concluded that the VASS investigated was effective on weekends during evening peak hours when there was traffic slow down. There was no statistical difference on any day of the week when there was no slow down. It was recommended, however, that further studies be conducted to evaluate more about the system.