. The elements of railroad engineering . ocking shouldbe not more than i^ miles.* In the New York subway express trains are run through blocksas short as 450 feet, and never more than 1000 feet long. The * For further details of block signalling consult signal companies catalogs andThe Block System by B. B. Adams {Railroad Gazette). 124 SIGNALING automatic signals and overlaps permit a train to proceed onlywhen the preceding train is at least in the second block a motorman undertake to run by a signal set at stop, anautomatic track device will engage a valve on his car, releasingt
. The elements of railroad engineering . ocking shouldbe not more than i^ miles.* In the New York subway express trains are run through blocksas short as 450 feet, and never more than 1000 feet long. The * For further details of block signalling consult signal companies catalogs andThe Block System by B. B. Adams {Railroad Gazette). 124 SIGNALING automatic signals and overlaps permit a train to proceed onlywhen the preceding train is at least in the second block a motorman undertake to run by a signal set at stop, anautomatic track device will engage a valve on his car, releasingthe air of the air brakes, and the resistance of the brakes stop-ping the car will run the current to the motors so high that theautomatic circuit breaker will act and cut out the current, thus, sofar as possible, seemingly avoiding dependence on the humanelement for safety. The subway is double tracked. ^f% tra Interlocking a Single-Track Crossing. — The figure shows asingle-track grade crossing of two roads. D indicates distant ®-®. — 6 Fig. 70 signal; H, home signal; S, deraihng switch; the numbers are thenumbers of the levers actuating the signals and switches, theselevers being concentrated in a single frame in the cabin or towerC. The levers are so interlocked in the frame that if the derailsof one line of track, say EW, are closed and signals 2 and i setat clear, the derail levers of line NS are locked open, and allother signals are locked at danger, the signalman in the towerbeing unable to change them until the cleared signals have beenrestored to danger and the derails of EW opened. The normalposition of all signals in this case being danger, the levers aresaid to be normal when holding the signals in their normal posi-tion, and reversed when holding them clear. So the derailswhen open are normal, when closed, reversed. Let a train comefrom E: the signalman, first — reverses lever 5, closing bothderails on EW, and automatically locking 6 normal; second —rever
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectrailroadengineering
