Evaluation of Arrow Panel Displays for Temporary Work Zones

The Oregon Department of Transportation evaluated the effectiveness of a “sequentially flashing diamond” arrow panel display as advance caution warning in temporary work zones. This display was evaluated by comparing it with two others; the flashing line and flashing four-corner. In survey responses from 33 state Departments of Transportation, each display was rated about the same in terms of effectiveness.

Field trials using each display were conducted in work zones set up on highway shoulders at two locations in Oregon. Total evaluation time at each site was nine hours, divided into three, 3-hour test periods. Each display operated for one hour during the 3-hour period. 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 (from baseline) for most 3-hour periods occurred when the diamond display was operating.

Motorists were surveyed about the three displays. People at a highway rest area were asked questions about the 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. However, 61% found the three displays confusing, particularly the line and the four-corner. Although there was evidence of confusion about the displays, 80% of the respondents said they would like to see the diamond used when work is taking place on Oregon highways.

The results of the field trials and motorist survey show considerable potential for the diamond display’s use as an advance warning device in temporary work zones.