Abstract: At 12:15 p.m. during the second week of construction of a 600 ft deep, third water tunnel for New York City, Employees #1 and #2 were brakemen on a train that had just unloaded a concrete load at the construction site. While returning to the loading area, their train collided with an oncoming, fully loaded train at approximately the 4,270 ft mark, after passing the California switching device at 6,000 ft. Employee #1 was removed to Long Island College Hospital, where he was pronounced dead at 2:25 p.m. Employee #2 was hospitalized at Bellevue with a fractured leg. Employee #3, the operator of the other train, suffered a minor knee injury but did not require hospitalization. This job was being done in two phases: the first consisted of digging and debris removal, and the second consisted of pouring concrete. The tunnel was approximately 29,200 ft long and had a single lane track for the majority of the distance. There were two areas, both approximately 100 ft long, where there were two lanes, and these areas, at the 6,000 ft mark and the 25,000 ft mark, were used for trains to pass one another. The method used to control the train traffic, near the double lane areas, was a California switching device.