Performance of Stimsonite Model 99-L2 snowplowable raised markers was evaluated during the 1975-76 winter at one urban and two rural locations; at the former, they were installed back-to-back for two-way traffic and plowing. This marker consists of a corner-cube retro-reflector mounted in a protective steel casting. The castings were found to be easily damaged by the cutting edge of tungsten-carbide snowplow blades, but essentially undamaged by steel blades. Vertical plow loads caused casting breakage where parts of the marker were cantilevered from the main section of the castings and where cross-sections were reduced. Serious reflector damage was observed. Field surveys and analysis of casting shape indicated that this damage was due to inadequacies in marker geometric design, allowing the snowplow blade to contact the reflector under some conditions. Casting redesign to place the reflector several inches behind its present position would probably correct the problem. Reflector retention in the casting was satisfactory. Although blade damage was observed, the tests were too limited to predict damage in widespread use. Night visibility was satisfactory in low ambient light conditions, but in high ambient light conditions it was marginal when the pavement was dry and unsatisfactory when wet. Photometric data indicated deterioration in reflector brightness to be similar to that reported by other agencies in non-winter conditions. Castings in back-to-back installations performed satisfactorily, but a single-unit marker with ramps on both ends would be simpler and more economical to install. /Author/.
Abstract