Zoo Interlocking Zoo Interlocking Tower, Philadelphia, Pa. This interlocking was the crowning achievement of the PRR’s use of fly-over trackage to manage a congested junction that was capable of routing a train in any direction on the PRR system. The complexity of Zoo has been reduced to some extent, but the tower continues to function full-time
Olentangy Interlocking Tower located on the east side of the Olentangy River not far from Spruce St. Columbus, OH. The camera is pointed southwest. The NYC (Big Four) is crossing, first the PRR's Bradford line and after passing the tower, the C&O.