ATSSA Signal September October 2020

The Signal | September/October 2020 23 Innovation • Factory-Installed Lights on Equipment, which are not recommended because they not only don’t provide adequate task lighting, but also produce glare, and should not be used when facing oncoming traffic. Presence lighting can enhance task lighting, while providing added safety benefits within a work zone. One of the most notable safety benefits is the documented reduction in aver - age driver speed in work zones where presence lighting is deployed during nighttime road work. The North Carolina Department of Transportation (NCDOT) studied work zone presence lighting on U.S. 17, and found that driver speed one mile down - stream of an active work zone without lights was 5.76mph higher than average speed downstream of a work zone with presence lighting equipment. Similar speed studies conducted in Tennessee and Michigan found that the average reduction of speed attributable to presence lighting ranged from 4.94 mph to 7.25 mph. NCDOT developed detailed presence lighting guidance for nighttime work zones on roads with speed limits greater than 55 mph or roads with high traffic volume. Presence lighting is specif - ically advised in areas where there is no task lighting, or where there is insufficient existing overhead light - ing. NCDOT guidelines address light output, elevation, installation, move - ment, location, and spacing of these light systems.  Case Study 4, Figure 2 – Presence lighting typical layout. (Diagram Courtesy of Ver-Mac Corp.)