Cab Signaling·

An explanation of the inception, By A. I-I. Rudd developn1ent, and extensive use of Chief Signal Engineer, cab signals on the P ennsylvania Pennsy I vania

IN 1922, th,e Interstate Commerce necessary, in order to stop the train the Pennsylvania signal system was Commission 'issued a tentative order, before it entered an occupied block, to based on three speeds, high, medium requiring 49 railroads to equip one provide two stop and one approach and low, the three-speed train-control engine division each with automatic signals back of each train. This made system was particularly applicable stop or speed control devices. Under it necessary to operate trains with at and was chosen for this reason. this order, on February 8, 1922, the least one block additional to that in vVhen the design of speed-control Pennsylvania presented a proposal general use between trains, or, using apparatus had been practically com­ for an installation of speed control on the usual signal arrangement, where pleted, the signal company represen­ 48 miles of single-track line between trains would receive an approach sig­ tative asked us if we wanted a cab Sunbury, Pa., and Lewistown. nal and then a stop sig·nal if the block signal, which would indicate a few The requirements laid down by the ahead were occupied, the automatic seconds before the apparatus on the commission included among others: stop device would have to apply at engine started to apply the brakes, 1. Automatic train stop : ·without each signal indicating approach, and there being a certain time delay be­ manual control by the engineman, re­ a train, instead of reducing to one­ tween the operation of the relay and quiring the train to be stopped, after half authorized speed at the distant that of the brake applier. vVe were which the apparatus may be restored signal and approaching the home pre­ advised that the cost would be only to normal condition manually and the pared to stop, would have the brake that of the cab signal itself and a little train permitted to proceed. applied every time it passed a distant wiring, as the apparatus for operating 2. Automatic train control or signal indicating caution or approach. it was already in place to work the speed control, which permitted maxi­ It was, therefore, quite clear that, control apparatus. We thought it mum-speed restriction, medium-speed under these requirements, the only would not do any harm and might be restriction and low-speed restriction device under which the P ennsylvania of some advantage to the engineman - a brake application in each case be­ could operate its heavy - traffic~ main­ by giving him a slight advance warn­ ing avoided if the speed were below a line divisions was some type of speed ing of what was about to happen, prescribed rate, but, if the low-speed control. and, as the purpose of the installation indication were not forestalled by a vvas to develop everything possible reduction in speed, an automatic stop Cab Signal Came As an Accessory in connection with the problem, cab would result. signals were installed. The indications The automatic stop was a simple The device installed on the Lewis­ given were "A", A uthorized ; "R", device, but, as the brakes would be town branch was knovvn as the loop Restricted; and "S", Slow. ~pp l i e d without any means of releas­ system, the control current passing *Abstract of a pa per presented before the mg them, whenever a train passed a through the rails and returning on New E ngland Railroad Club, Boston, ·Mass., signal indicating stop, it would he the lin e wire known as the loop. As on A pril 14. 266 RA I LWAY SIG N A LING May, 1936 It was decided that, although not from the engineman, if he is alert, placed in service between Manhattan required for the operation on the and that any device which did so re­ Transfer and Millham Junction on Lewistown branch, we would arrange move his control and applied the December 10, 1929, and between Mill­ the installation for three-block con­ brakes in the same way, regardless of ham Junction and Philadelphia on trol down-grade and two blocks up­ the speed, size or weight of the train, August 4, 1930. grade on the same track, restriction was undesirable. on curves, enforcement of slow speeds Under the revised ruling, the auto­ Cab Signal Recognized by I.C.C. through two towns, in conformity matic stop was less objectionable in with local ordinances, and automatic that the engineman, if he were alert, Early in 1929, following an accident cut-in and non-automatic cut-out, at could prevent it from operating, and at Short Lane on the Maryland clivi­ the ends of the equipped section. In the experience on the Lewistown sian, the Interstate Commerce Coni ­ fact, every complication and concli­ branch had convinced many of us mission suggested that we consider tion to be met on our system that we that the cab signal was the real an­ automatic stops or cab signal installa­ could think of was reproduced, except swer to the problem, because it would tion in this foggy territory, this being only the effects of brake applications tell the engineman the conditions the first time they recognized the cah on heavy freight trains. ahead, advising him of any change, signal as a proper device to suggest. The installation was made without and permitting him to control his C;b signals from Philadelphia to wayside signals except those located train as his judgment dictated. The \Vashington, D. C., were authorized where it was necessary to stop and installation on the line between Balti­ on February 27, 1929, and completed hold trains, and these signals indicated more, Mel., and Harrisburg, Pa., au­ from Baltimore to Washington on either stop or proceed. On the western thorized on January 14, 1925, was January 15, 1930, and the installa­ half of the branch, what was known begun in April, 1925, and had to be tion from Philadelphia to Baltimore as the modified A.P.B. system was in­ completed by July, 1926. Therefore, entirely completed on February 8, stalled, by which the train itself, if the same system was installed as was 1930. the conditions were right, set up the used on the Lewistown branch, ex­ In order that our engines equipped combination by which it would receive cept that, instead of the speed con­ with cab signals, stop and forestaller, clear signals, and an opposing train, trol, stop and forestaller apparatus operating between Pittsburgh and stop signals; while on the eastern was placed on the engines, the way­ Columbus, might have this protection half we used what was known as the side apparatus being identical, and throughout the run, wayside apparatus dispatchers' remote-control system, by except that we were permitted to was placed in service early in 1930 which the operator at Sunbury set up equip one locomotive with two cab between Newark, Ohio, and Colum­ the proper combination in the way­ signals, one for the engineman and bus on the C. & N. division of the side apparatus. This was the fore­ one for the fireman and substitute a Baltimore & Ohio. The installation runner of the centralized traffic con­ whistle for the automatic stop. The on the Pittsburgh division was com­ trol now in use on several railroads, whistle was a small one and only pleted on November 16, 1930. Mean­ including the Pennsylvania. sounded for a short time whenever a while, the New York & Long Branch From the foregoing it will be seen more restrictive indication was dis­ equipped its line from W ooclbriclge that the cab signal was a by-product played. Junction to Bay Head Junction with of the speed-control devices, being four-indication cab signals, stop ancl developed in connection with this Coder System Developed forestaller, placed in service on May speed control. The installation on the 31, 1928. Lewistown branch was completed and Meanwhile, the Union Switch & On March 26, 1935, wayside ap­ placed in service on July 11, 1923. Signal Company had developed what paratus was placed in service on the is known as the coder system, which Perth Amboy and W ooclbriclge Use of Forestaller Permitted required very different engine and branch, filling in the gap between New wayside apparatus, and provided four York and Bay Head, and on May 3, On July 18, 1924, the commission indications instead of three, in the 1935, work was finished on the freight changed its order covering the auto­ cab. This was tried out for the first line from Landover, Mel., to the north matic train stop, which read "With­ time on a specially equipped MU portals of the Virginia Avenue tun­ out manual control by the eng·ineman train on the Philadelphia division nel, Washington, D. C. requiring the train to be stopped, after on July 15, 1926, the wayside ap­ We now have cab signals on our which the apparatus may be restored paratus being superimposed upon the main line from New York to Wash­ to normal condition manually and the existing signal installation. The re­ ington, from Atlantic City to Cam­ train permitted to proceed," by add­ sults were so satisfactory that it was den, and from New York, Atlantic ing an alternative paragraph reading deciclecl to use this scheme on the City, Philadelphia, Baltimore and as follows: "Under control of the \lV est Jersey & Seashore between Washington to Indianapolis, except engineman who may, if alert, fore­ Camden, N. J., and Atlantic City, and between Philadelphia and Harris­ stall the application of the brakes by 011 the P. C. C. & St. L. between burg, and our alternative line through the automatic train-stop device and Columbus, Ohio, and Indianapolis, Dayton (between Pittsburgh and control his train in the usual manner Incl. Columbus); also from New York to in accordance with hand signals or O'n January 14, 1924, the Inter­ Bay Head via our line and the New under limits fixed by train order or state Commerce Commission ordered York & Long Branch, and on the prescribed by the operating rules of additional installations, the Pennsyl­ Long Island from New York to Port the company." vania selecting the Middle division, Washington, N. Y. and Jamaica to This changed the entire picture as Harrisburg, Pa., to Altoona, and an­ Babylon. far as the automatic stop was con­ other division on the P.C.C. & St. L. cerned, in that, by forestalling, the between Pittsburgh, Pa., and Newark, Cab Signal and ·whistle Replaced "double red" or the non-release brake Ohio. · Automatic Stop application at the distant signal was Early in 1927, a voluntary installa­ not required. It has been and is the tion of cab signals, with whistle and On February 6, 1931, the Inter­ feeling of our people that the control acknovv ledg-er, was recommended on state Commerce Commission grantEd nf the train should not be taken away the New York division; it was finally (Continued on page 268) 268 RAILWAY SIGNALING May, 1930 the signals, and the 100-cycle inter­ rupted current for operating the cab signals; and, · in such cases, two som-ces of supply are used, except where all is 100-cycle. The original coder system had been designed for The comrol interlockings. (Continued from page 266) Double-Heading Feature us permission to operate cab-signal and continue to sound until acknowl­ Developed (whistle and acknowleclger) equipped edged by the engineman or fireman. locomotives, if used in inter-divisional The same action was required to ac­ Our motive power people developed runs, over territory where the auto­ knowledge the signal as to forestall another important improvement, by matic stop had been ordered in, and the stop. arranging the apparatus so that cab on December 12, 1932, permission to Only one cab signal per engine was signals are now operative in the sec­ remove the stop and forestaller from used on the Lewistown branch and ond electric engine of a double header all locomotives, substituting therefor but one signal was also used in the or even on a third or fourth engine the whistle and acknowleclger. This loop system between Baltimore and coupkd. The cab signal, supplement­ work was started at once, with the re­ Harrisburg. When the coder system ing and co-ordinated with the fixed sult that on February 15, 1933, all was adopted on theW. J. & S., giving signals along the road, is a great help active equipment was in operation indications: "Proceed," "Approach to the engine crew, especially in fog with the Union Switch & Signal Com­ Restricting," "Approach," and "Cau­ or storm when the wayside signals pany's coded continuous automatic tion Slow Speed," it was decided to may be partially obscured some dis­ four-indication cab signals, with put in two cab signals, one for the tance away; by changing its indica­ whistle and acknowledger. engineman and one for the fireman, tion if conditions change, it expedites traffic if an occupied block ahead is The acknowledging device was the and this has been the standard since. cleared. It also provides an added same as that required for the fore­ safeguard if track ahead is ob­ stalling of the automatic stop, but, Code Developed for Control instead of the latter, a deep-toned of Wayside Signals structed after a train has passed a vvhistle was provided and the circuits wayside signal indicating proceed. There usually are two types of cur­ so arranged that, whenever the cab *For explanation of this installation see signal changed to a more restrictive rent in the rails, a-c. 60-cycle or 100- page 205 of Railway Siguali11g for May, indication, the whistle would. sound cycle constant, or d-e. for operating 1935.