Mobile Traffic Signals in Lieu of Flaggers for Moving Operations

Flagging in work zones is crucial to the safety of workers and drivers, but it is one of the most dangerous tasks, representing more than one-third of injuries to pedestrian workers (Odell 2013). Automated Flagger Assistance Devices (AFADs) are portable traffic control systems that can help to improve safety because flaggers can operate them from outside the flow of traffic. Several states have evaluated AFADs, with generally positive assessments of their effectiveness. While compliance with the AFAD is not universal among drivers, violation rates were lower than red-light violation rates documented in other literature (Finley 2013). The Minnesota Department of Transportation (MnDOT) requested information about self-propelling AFADs for mobile work zones, with the specific idea of mounting an AFAD on a remote-controlled caravan mover. CTC & Associates spoke to or emailed staff at the state departments of transportation (DOTs) in Iowa, Missouri, Montana, Oregon, South Dakota, Texas and Wisconsin as well as representatives of the Transportation Research Board Committee on Work Zone Traffic Control, the Smart Work Zone Deployment Initiative and the American Traffic Safety Services Association. None of the state DOT representatives said that their states currently used or planned to implement any self-propelled AFADs. In fact, most of the states have not implemented any form of AFAD, although some are beginning to investigate the possibility. None of the individuals interviewed were aware of any examples of self-propelled AFADs in use in other jurisdictions. However, some research has been conducted on robot-controlled traffic cones and road signs at the University of Nebraska–Lincoln Robotics and Mechatronics Lab. This project (Farritor 2005) developed a working system of eight self-propelling safety barrels and one road sign, all controlled by a single lead robot. While the system was functional, it never became commercially available. MnDOT's idea of a human-controlled, self-propelling AFAD operated by remote control represents a simpler system that is likely feasible from a technological standpoint. A procedural issue was raised that would likely need to be addressed if MnDOT implemented a mobile AFAD. In a moving work zone, one of the devices would be traveling with traffic while the upstream device would be traveling against traffic. In moving work zones with human flaggers, that problem can be solved by using a third flagger. Two flaggers would be positioned on the upstream side, and they would leapfrog each other rather than attempting to move against traffic. One respondent questioned the practicality of a self-propelling AFAD because temporary signs and devices would need to be moved as well. Stationary AFADs are generally well understood by drivers. CTC & Associates found no information that suggests whether a moving device would be equally well understood.


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  • Accession Number: 01601705
  • Record Type: Publication
  • Created Date: May 31 2016 1:55PM