Rotary beacons were initially used in the early 1960s to make switchers more visible in large yards at night. The flashing lights helped the vardmasters in the towers keep track of the switchers. In the 1970s, the Federal Railroad Administration began studying ways to reduce grade crossing accidents by making trains more visible to motorists. Tests with oscillating headlights, rotating beacons, alternating flashing lights, ditch lights, and roof-mounted strobe lights led to the use of a triangular combination of two strobe lights with a standard headlight or a pair of roof-mounted strobe lights. More FRA testing followed in the early 1990s to identify the most effective combination of a normal headlight with various secondary lights. In 1993, a triangular configuration with alternately flashing lower lights was field tested on CalTrans, Conrail, and Norfolk Southern. At the end of the tests, the FRA report lists an accident reduction of 76.4 percent on CalTrans, 74.3 percent on Conrail, and 54.6 percent on Norfolk Southern.
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