US SIGNALLING TOWERS

by Mike Brotzman

1. Bryn Mawr

The tower at Bryn Mawr sits on the Main Line. This was the ex Pennsylvania RR east/west main from Philadelphia to Pittsburgh. In 1915 this 4-track line was electrified about 20 miles to Paoli. With easy MU transport into the city the main line quickly became the home of the social elite. Bryn Mawr tower was most likely built around 1915 and it served as a block station. In this function the tower controlled the 6 switch cross over and the local signals.

Bryn Mawr is built in the classic PRR style with a bay window, brick base, cream wooden second story, slate roof and internal staircase. Bryn Mawr is a fine example of second-generation PRR towers. This brick wood combo supplanted the all wood 1890's version. Bryn Mawr ceased operation in 1994 due to a fire and you can see the new remote interlocking to the left of the tower. The ramp on the right is for handicap access to trains. In the US only the interlocking gets the name plate and because the tower is no longer in service the Bryn Mawr sign has been transferred to the new relay sheds.

In this rear view you can see the chimney and roofline. Bryn Mawr was a pneumatic interlocking. Instead of using levers and wires or pipeline there was most likely a Union Switch and Signal Electro-pneumatic interlocking machine. You would push a button and it would send a blast of air to operate the switch. The current interlocking is still pneumatic. In this picture you can see one of the 1911 catenary poles. They have been painted to match the copper wire.

Here is a view from farther down the platform. The yellow wooden palettes on the tracks are to facilitate access to the inner tracks. In the distance you can see the signals. There is a signal bridge and a black signal mast on the tower side. Amtrak still uses the former PRR position light signals. Each round signal has up to 7 yellow lights. A vertical line is clear, diagonal is caution and horizontal is stop. The signals on the bridge have 2 aspects to convey such information like go slow, go less slow, stop then go, etc. (Check out the signal rules page at Eastern Railroad News for the complete list of aspects. This link is in the "links" section I believe.) The mast signal was showing clear when I took the picture and I have enhanced it slightly for better visibility.

This last shot does not show the tower, but it does show the 1915 Bryn Mawr sub-station. You can also see the eastern signal-bridge. The line is not have bi-directional signaling and the signals only face the flow of traffic. The rest of the line is controlled by automatic block signals. At this point the line retains the PRR 152 lb./yard jointed rail. The rail is old and badly bowed in the middle so new welded rail is being installed. Amtrak's Harrisburg line is one of the few lines with enough traffic to warrant signal towers. From Paoli to Philly Amtrak shares the line with SEPTA which provides MU service. At rush hour there is a train every few minutes. The remaining towers on the Harrisburg line include ZOO, Overbrook, Bryn Mawr (closed), Paoli, Thorn (Thorndale), Park (Parksburg, closed), Cork (Lancaster) and State (Harrisburg). Bryn Mawr's operations have been transferred to Paoli.

All photographs are copyright © Mike Brotzman

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