Arrow Panel Display Evaluation in Temporary Work Zones

The Oregon Department of Transportation evaluated the effectiveness of a “sequentially flashing diamond” arrow panel display as an advance caution warning in temporary work zones. This display was evaluated by comparing it to flashing line and flashing four-corner modes. When surveyed, 33 state transportation agencies rated each display about the same in terms of effectiveness. Daytime and nighttime field trials using the three modes were conducted in two work zones set up on highway shoulders. Nine hours of evaluation time at each site was divided into three, three-hour test periods, with each display operating for one hour. Hourly average and 85th percentile speeds recorded during the tests were lower than corresponding hourly baseline speeds for all display modes. The greatest speed reductions occurred when the diamond display was operating.
Additionally, motorists at a highway rest area were surveyed about the three displays that were operating in the parking area. Over 70% of 274 respondents chose the diamond display as the most effective at getting their attention, and 80% said they would like to see the diamond used when work is taking place on Oregon highways. However, 61% found the three displays confusing, particularly the line and the four-corner. The results of the field trials and motorist survey show potential for the diamond display’s use as an advance warning device in temporary work zones.