Differences in Nighttime Luminance of Work Zone Drums with and without Steady-Burn Warning Lights

Abstract

Research was performed to explore the differences in the nighttime luminance of drums, with and without steady-burn warning lights, that are used in work zones to channelize traffic. Two evaluations were performed: one in the field, which included luminance measurements of 372 drums in 15 freeway work zones throughout Michigan, and another, controlled evaluation, which included luminance measurements of 24 common drum scenarios in a vacant parking lot. Drums with and without steady-burn lights were considered in both evaluations. All luminance measurements were performed from the passenger seat of a vehicle under low-beam headlamp illumination. The results of the controlled evaluation showed that the addition of a steady-burn warning light increased the average luminance of drums with high-intensity sheeting by 0.165 candelas per square meter (cd/m²) (2.6%). The added light increased the average luminance of drums with microprismatic sheeting by 0.50 cd/m² (3.9%). Similar results were obtained during the field evaluation. It was concluded that drums with high-intensity sheeting and without steady-burn warning lights typically provided adequate levels of nighttime luminance when viewed from a vehicle under low-beam headlamp illumination. If additional nighttime brightness was desired, however, microprismatic sheeting offered far greater luminance than a steady-burn warning light.