This study investigated the effectiveness of various barrier-mounted reflectors. Barrier delineators come in different shapes and sizes, and their materials and installation labor costs also differ. They can be mounted on the barrier top, the barrier face or even on the pavement. A delineator's level of effectiveness depends on the type of delineator as well as its placement.
This study evaluated the effectiveness of seven concrete barriers' delineators: Astro-optics on the barrier top, Reflexite on the barrier top, reflective cylinders on the barrier top, hazard panels, raised pavement markers on the barrier face, Astro-optics on the barrier face, and Davidson markers on the edge line.
The study included a literature review, observations of the delineators at a test site, and having motorists drive by the delineators and rate them.
The study concluded that drivers need the guidance of delineators most when they are confronted with opposing traffic headlight glare. Devices placed on top of the barrier are washed out by headlight glare and therefore are not effective. The best placement of concrete barriers is on the barrier face. A delineator loses more than half of its reflectiveness in a short period due to dirt accumulation.
The study recommended that the Manual on Uniform Traffic Control Devices make note of the effect of opposing traffic headlight glare on delineators' effectiveness, that delineators be placed on the top of concrete barriers, that prism-lensed devices are the most effective, and that delineators should be cleaned regularly.