The results of this study are generally mixed. First, it is clear from the data that the low power benefit of LED lights can be realized under specific conditions. For similar visibility conditions, the LED lights performed as well - or in some cases better - than the HID strobe. Viewed directly from the rear, side, or front of the plow vehicle, it appears that LED-based strobes can be made to be equally conspicuous while reducing the costs associated with high power, maintenance, and reliability issues.
However, the above benefits are limited by the problems associated with angularity of the LED lights. The LED lights were shown to be equally conspicuous as the standard strobe at well-defined angles only. The reduced conspicuity at off-angles is a direct result of the angular intensity variation of the LED devices due to the lenses used to increase the intensity at the front, back, and side of the plow vehicle. Decisions must be made regarding the requirements of visibility at off-angles in order to determine if LED lights can be made to meet the needs of Mn/DOT. If the expectation is that conspicuity comparable to the standard strobe is needed at all angles, LED lights must be designed to meet those needs. However, if conspicuity at limited angles is acceptable, then LED fixtures are already on the market that meets those needs.
This work was done by Tim Vogt and Kenneth Miller of St. Cloud State University.
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