Steven D. Schrock
About the research
In long-term work zones on multilane highways and/or freeways, the Federal Highway Administration has interpreted the Manual on Uniform Traffic Control Devices to mean that only one advance warning arrow displays can be used to denote the closure of a single lane. Where two or more lanes are closed, a single arrow display is used for each lane to be closed. However, in short duration, mobile, and moving work convoys the MUTCD allows the use of multiple arrow displays to indicate a single lane closure. These disparate uses for arrow displays create the potential for confusion by drivers.
This paper describes the results of four focus group interviews with Midwestern drivers. Participants were shown several mocked images of shadow work vehicles with arrow displays and were questioned on how well they understood and/or interpreted the message conveyed by arrow displays depending on the display type and quantity of displays used, and looked specifically for potential driver confusion.
Focus group participants generally considered panel displays that included motion (e.g., sequential arrows and sequential chevrons) as implying a more important situation and preferred their use over flashing versions. While participants were receptive to the use of multiple arrow displays on multiple shadow vehicles, a minority indicated that this conveyed a need to move over more than one lane. Participants also indicated that staggering sequential shadow vehicles from the shoulder into the closed lane provided useful information as to the number and location of the closed lanes.