Chicago's Newest Subway Has

Automatic Block Signaling and Stop

Rapid transit on the Milwaukee ave trains run on a seven-minute head way. Owl trains, from 1 a.m. to 6 nue subway running on a two and one-half a.m., are two-car trains, running minute headway are protected by automatic every 30 minutes. All trains stop at all stations. The signal system how train stops and automatic block signaling ever is designed for a lit minute headway to take care of traffic when in the future connections are made 'S Milwaukee-Dearborn- 15 minutes in going from Logan with elevated lines from the west at Congress subway is equipped with Square to downtown. Congress and Lake streets. automatic devices and Although construction of the sub automatic block signaling as well as way was started before the war, the Layout station and grade time control which emergency's shortages of materials The Milwaukee avenue subway provides an even flow of traffic over and men halted the work. After the (Route No. 2) is double track all the the line. This subway is Route No. 2 war, work was resumed and the sub way from Congress street station to of the Chicago Subways and extends way was opened to operation in the end of the elevated at Logan for 3.99 miles from its connection February, 1951. Square. There is a diamond cross with the Logan Square elevated near over at the end of the station plat Damen avenue to the Loop. From Traffic form at Congress street station with near Damen avenue, the subway During rush hours, Monday four electro-pneumatic switch ma runs southeast under Milwaukee through Friday (7 a.m. to 9 a.m. and chines. These switches and their avenue to , east under from 4 p.m. to 6 p.m.), six-car trains associated signals are controlled by Lake to Dearborn, south under ran on a two and one-half minute a Union "UR" route ma Dearborn to Congress and west un headway. At other times during chine located in a tower at the east der Congress to its terminal near week days, four-car trains run on a end of the station platform. La Salle street. This subway is sav four minute headway. On Sundays, There are two emergency cross ing riders an average of holidays and evening hours two-car overs on the line located at Hubbard

176 RAILWAY SIGNALING and COMMUNICATIONS MARCH, 1952 street in the subway and on the elevated line just south of Damen avenue. Switches for these crossovers are hand-thrown, using a switch- and-lock mechanism equipped with electric locks. Automatic Block Signaling Automatic block signaling is used throughout the subway and on the elevated to Damen avenue. Signal ing is arranged for one direction run ning only, and trains normally use right-hand running. The signals are the vertical color-light type, with the conventional red, yellow and green aspects. Interlocking home signals have two "heads" each consisting of three lights in a vertical row. Below each "head" is an illumination number plate bearing an X and the lever number. A letter "A" is placed un der die top "head" and a letter "B" under the bottom "head." For ex ample (see Fig 4) signal 22 has two illuminated number plates, the up per one reads X22A and the lower Interlocking control machine is "UR" route type with a line-of-light track layout one X22B. motormen may be able to see signals train ahead. Yellow indicates pro On home signals in the approach at all times. ceed with caution prepared to stop to diverging routes, the upper signal at the next signal. And green indi Aspects "head" controls the through route, cates proceed. A lunar white marker and the second "head" controls the A red aspect indicates Stop and is used on the grade-time signals, diverging route. Approach signals, proceed prepared to stop within a This light indicates that the grade- located within the approach locking train length, and requires that the time control is in operation, as will limits, are also lever controlled. All motorman stop his train and release be explained later in the article. A approach, block and home signals the automatic train-stop trip. The red-over-red-over-yellow aspect is a are at the right of the track gov motormen are not to key-by a stop call-on, used only on the home sig erned. Repeater signals are in use signal unless they have waited about nals at the Congress street inter on curves, being placed on the left one-half minute and are then rea locking as will be later described. of the track they govern so that sonably satisfied that there is no Automatic trip type train-stop de vices are installed at all signals ex cept repeater signals. These trips are "T" shaped devices which are at track level and are on the side of the left running rail. They are de pressed one-half inch below the top of the rail when the signals, with which they are associated, display either a green or yellow aspect. When the signal is red, the trip pro jects approximately 37/i« inches above the top of the rail. If a train is run past a red signal, the trip strikes a lever on the left side of the leading truck of the car whch causes the brakes to be applied in emergency. In normal operation, for example, a train approaches a red signal. The motorman stops the train with the front of it just short of the signal, so that he may reach out of the cab window and operate a trip release lever on a bracket projecting from the signal mast toward the ap proaching train. When the motor- man operates this release the trip is depressed. The train can then pro Fig. 1 Map showing route No. 2 of the Chicago Subways ceed without having the brakes ap

MARCH, 1952 RAILWAY SIGNALING and COMMUNICATIONS 177 signal 6. Consequently the stop at signal 12 where track sections e, f signal 5 must also be in the tripping and g provide the length for braking position. Trains then are kept two a train at restricted speed when sec blocks apart when running under tion h is occupied as shown on the caution signals. This does not affect diagram by a solid line. The dotted track capacity in free running terri portion of this line represents two tory where blocks are often longer timing sections c and d. The remain than the minimum length. However ing grade time signals 9 to 12 have on descending grades the block the same controls. An illuminated

Rear view of a train standing in the sta tion with the signal showing a red aspect and the train-stop trip in the raised position

lengths at maximum speed would sign at the beginning of the timing be prohibitive, also normal block section for signal 8 informs the lengths keep trains too far apart at motorman the restricted speed at station stops. In both of these cases which he must run to allow sufficient trains are closed in to obtain greater time for time element relays to clear track capacity by restricting their the signals. The grade time signals Front view of a track-side relay case speed. This can be safely done by normally indicate red with the train means of time controls. stops in the tripping position to en force the speed restriction. plied by the operation of the train- Crade Time Control Signal 7 has no time control, is stop trip. At a home signal the call- Maximum grades are three per not a grade time signal and the sec on aspect must be displayed before cent where the subway goes under tions d, e and f within its control the above operation is effective. the and where it joins limits will vary in length depending the elevated structure. Elsewhere on the maximum speed an approach Track Capacity the tracks are almost level (as they ing train can attain. The minimum block length is the are in stations) with a variation in Signals 7 to 11 inclusive each have distance necessary to stop a train grade, for drainage purposes, of only a lunar-white marker which may be at its maximum attained speed with one-half of one per cent, or less. displayed only with its respective an emergency application of the Referring to Figure 2 the grade signal showing a caution indication. brakes plus a factor of safety. In time control operates in this man This marker informs the motorman normal automatic block territory ner; consider signal 7 located at the that, if displayed, the next signal is signal controls have a one block top and signal 12 at the bottom of red because of time control only and overlap due to the use of train stops. a descending grade with the inter if dark, that the next signal is red Referring to Figure 2 a train in block vening signals spaced on short because a train is within its control sections b and c would not have full blocks or rather sections of a block. limits. protection from the train stop at The control for signal 8 extends to A train in track section c travel-

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HO- 4^ -tO- HQc-Tirne sign |— g — r 6 751 Legend 8 6T ' 9 6T 1 10 CT 1 II GT 12 GT — Ti'meSignal con+ro! con+rol Train stop depressed In +ri p ping position Fig. 2 Diagram showing grade time control signals

178 RAILWAY SIGNALING and COMMUNICATIONS MARCH, 1952 ing at the prescribed speed will al begins. With a train standing at the low sufficient time to clear signal 8 station a following train running at to a caution indication, permitting its maximum attained speed would signal 7 to change to green immedi be tripped at signal 21 and be ately in front of the train. The re stopped short of signal 23. However maining grade time signals will clear if the train travels at or under the in a like manner as the train pro permissible speed in track section a, ceeds down the incline at or under then a time element relay will oper the permissible speed. The motor- ate to cut off the extended control

Front view of a subway train standing in one of the stations

man may elect to take a longer time of signal 21 and permit it to clear to to brake his train and accept signal caution. Then as the train at the sta 7 at the caution indication. He then tion moves ahead and the second will have another opportunity to train runs slowly enough in section consume the required time in sec b to cut off the extended control for tion d, then both signals 8 and 9 will signal 22 which permits it to clear clear to caution whereupon signal 8 as soon as the first train is off of sec will change to green. tion d. In this manner one train can closely follow another into a station Station Time Control area. Speed restriction is enforced Rear view of a track-side relay case by the train ahead setting the signals There is a continuous center plat to the stop indication. With no train tube, relays are in cases placed near form the entire length of that por ahead, as in non-rush hours, the ex the signal and equipment with tion of the subway under Dearborn tended controls are effective and the which they are associated. street, having three station stops for signal circuits are so designed that each track. Considerable time is con the timing relays do not operate. Track Circuits sumed in loading or unloading in this downtown area, consequently Plug-In Relays The Milwaukee avenue subway trains would be delayed during rush trains operate on 600 volts d.c. using hours were it not for station timing All relays are the plug-in type. No a as positive and one of which keeps trains running closely polar relays are used. The track re the track rails as the negative return. together at restricted speed. lays are the a.c. vane type operating The other track rail is used as the Referring to Figure 3 signals 21 on 60 cycles. Time-element relays signal rail for a.c. track circuits. In to 25 inclusive are station time sig are the Union PT-55, which are the sulated joints are used in only the nals with their controls showing a ratchet type with adjustments of signal rail. At the feed end of a dotted timing track section to the time from 2.5 sec. to 25 sec. These section, one wire from rear, a solid line for the station time relays operate on 16 volts d.c. from the secondary of a track transformer control and an extended dotted por a coding unit which sends out a d.c. is connected to the signal rail and tion for the control without station code of 240 cycles per minute. the other to the negative track rail. timing. An illuminated sign informs Relays are on racks in relay rooms At the relay end of the track circuit, the motorman where time control at the stations, and on the line in the one side of the a.c. vane type relay

21 ST 22 ST 23 5T 1 24 ST l 25 ST 1 2.6 27 Fig 3 Diagram showing station time control signals MARCH, 1952 RAILWAY SIGNALING and COMMUNICATIONS 179 is connected to the signal rail and is indicated on the control machine signal control circuit or equipment, the other to the negative return rail. at La Salle-Congress interlocking. and, at the same time, power to Advantages of the single-rail a.c. Compressed air for the operation other controls is not cut off. type track circuit are that no im of the switches and train stop Interlocking Machine pedance bonds are needed and the mechanisms is provided by a com track circuits can end at a rail end, pressor plant at Damen avenue sta The interlocking machine at the thus eliminating unnecessary cutting tion. Also there are two cross-con Congress street station is the "UR" of the rail. nections with the air lines of the route type, with a control machine subway, so that com containing a line-of-light track lay Power Supply and Distribution pressed air is always available. A l'A out, and knobs which can be pushed Power for the signal system is fed in. air line is in each subway tube to or turned for selection of routes from several points along the line provide air for equipment on each through the interlocking, and levers from commercial sources. At the in track. Compressors are rated at 150 for auxiliary operation of switches. terlocking tower at Congress street cu. ft. per minute and there is a low The control machine is also equipped with a row of red indicating lights warning of low air pressure, inter locking power interruption, auto matic power interruption, and Plug-in relays and grounds on interlocking ground de automatic ground tector and automatic signal ground detector ( third unit detector. When one of these units from right in sec ond row of relays) operates or power fails, the corres mounted above cur ponding red light is illuminated and rent limiting resis a bell rings. A pushbutton under the tors on a panel light will stop the ringing bell. There is also a maintainer's call but ton on the panel.

and at certain other points, there is a power and relay room where trans formers are connected to normal and reserve commercial sources by Terminal board in means of a transfer switch. This one of the relay automatic transfer switch will cut in rooms with cur rent limiting resis the reserve commercial source if the tors and pair of main source of supply should fail, rectifiers (lower and will automatically return to the right in the picture ) main source as soon as the failure has been corrected. Overload pro tection equipment is also installed on the power lines. The a.c. power at 110 volts single-phase is dis pressure air alarm at the Congress To initiate a route, the operator tributed locally through each sub street interlocking tower to indicate pushes a knob on the track diagram way tube on a two-wire line of No. when the air pressure falls below 85 at the point representing the signal 6 wire. Signal lighting and track cir per cent of normal. where the train is to enter the route. cuit operation is a.c. Pairs of recti A red light will appear in the signal fiers paralleled on the output side Current Limiting Resistors indication light at that knob and are used to convert the 110- volt a.c. In Control Circuits short sections of white light will ap to 16-volt d.c. for the signal control There are 100-ohm resistors in pear on the track diagram at each circuits including the controls for series with 1600-ohm relays (PN-50 available exit. The operator then the electro-pneumatic valves for the or PN-50B), and 30-ohm resistors in pushes the knob on the track dia switch and trip mechanisms. This series with the LP-58 relays. Some gram representing the point at 16-volt d.c. is distributed through 20-ohm resistors are used in other which the train is to leave the de No. 6 wire in aerial type two-con operating circuits. If a short circuit sired route and then, if conditions ductor cable run with the two-con occurs in the control circuits, it will permit, the switches will be posi ductor 110- volt a.c. power supply cause the circuit to be inoperative, tioned to line up this route after line on messenger wires on the walls but will not blow the power supply which a continuous white line of of the tunnels and under the station fuse. This will prevent a serious tie- light will be displayed on the track platforms. Also included in each up in traffic on the subway. Experi diagram from the entrance to the power room are automatic ground ence has shown that current limit exit points of the route. Before each detectors for each d.c. and each a.c. ing resistors are feasible. The short switch has reached its proper posi power feed. Operation of the trans is capable of being found by the tion, a flashing red light appears in fer switches and ground detectors maintainer without damage to the the diagonal section of the crossover

180 RAILWAY SIGNALING and COMMUNICATIONS MARCH, 1952 including that switch. Normally these switches take two or three sec onds to operate but should a switch be obstructed or for any reason fail to complete the desired movement, this continuous flashing red light would call the operator's attention to that fact. After the route has lined Transfer switch up, if conditions permit, the trip at automatically the entrance to the route is cleared cuts in reserve and the signal at the entrance to the commercial route will display the proper pro source of power if main power ceed aspect, after which the light at supply fails the entrance knob on the track dia gram will change from red to white. As a train enters the route, the track circuits occupied by the train show up as red, and when the train leaves a track circuit, the red is ex tinguished. The route is automati cally cancelled as the train proceeds through the interlocking. However, if the operator wishes to keep a route for a following train he may clear, the motorman starts the train. the signal is in the tripping position, push and turn the entrance knob The starting lights will not illumi and no train is between the ap thus establishing a route that will nate unless the route for leaving the proach limits and the home signal; not cancel with the passage of the station has been established by the if the train is on the releasing track train. To cancel this route, the op tower operator, and the next train section; or if the automatic time-ele erator must turn and then pull out arrow has been displayed for that ment relay (set to operate at 20 sec the entrance knob momentarily. side. The arrow is extinguished onds) has picked up. On the desk portion of the control when the starting lights are dis To restore a route with a train in machine is a box containing two played and the starting lights are the approach circuit the signal must buttons with associated indicating extinguished when the train leaves. be set to give a stop aspect then an lamps that are used to illuminate an To set up reverse routes on the automatic release will operate for arrow on the platform sign for the machine, such as moves through 20 seconds to unlock the route. An next train out of the station. When signals 24 to 22, 24 to 8, 22 to 6, and auxiliary switch lever for each cross the operator pushes one of these but 8 to 6, the operator must hold the over if placed in the normal or re tons, an arrow on a sign over the entrance button in, while he pushes versed position will cause the platform is illuminated, which points the exit button. Thus it is not likely switches to move to a corresponding in the direction of the train next that the operator will inadvertently position if free to do so because of leaving the station. An amber lamp initiate a reverse route when setting electric locking. If locked a release lights on the control panel to indi up a normal route. On a small panel, button can be pushed and then cate that the arrow is lighted. Next such as this one, the operator has no pulled where upon a time release the operator lines up the route for difficulty in reaching both ends of relay will operate for 20 seconds to the train by pushing knobs for the control panel in order to estab release the switch locking. The routes 22 to 24 or 8 to 24, depend lish a reverse route. switch machines are restored to ing upon which track the train is route control by placing the auxili ary lever in its central position. standing. When the route is estab Locking lished it shows as a white line on All interlocked home signals have the control panel, and the green The interlocking is provided with a call-on aspect which is red-over- starting lights on the platform are sectional route release locking as red-over yellow. The yellow is nor illuminated. Also a single-stroke well as approach locking and time mally dark, and can only be illumi bell is sounded to indicate to the locking. Approach locking of a sig nated by the operation of the call-on train crew that the route is estab nal releases: if the signal is restored button by the tower operator after lished and the train may leave. to stop and the train-stop device at the route has been lined up as previ- The starting lights are located on brackets suspended from the roof on over the platform. There are three O-l of them, one opposite the place taken by the conductor of a train between the first and second cars S+ation and between the third and fourth pla+form cars. A third light is located at the east end of the platform in view of the motorman. However, the usual 22 r procedure in starting a train is for • Red -N- the conductor to give the motorman two short buzzes on the train com * Yellow- red | municating system after the doors © Green - yellow - red |i are closed. If the train starting lights O Automatic signal are illuminated and signal 22 or 8 is Fig. 4 Diagram of track layout and signals at Congress street interlocking

MARCH, 1952 RAILWAY SIGNALING and COMMUNICATIONS 181 ously described. Hence any train ap already west of signal D47. But this release has run down (one minute) proaching a home signal at the in route will show as flashing white on the electric locks on all the switches terlocking, such signal showing a the control panel. When the train in are unlocked and a padlock on each red-over-red aspect, the motorman is the station moves down into the switch can be unlocked and the not able to manually release the trip storage area beyond the platform, switch moved. mechanism, thereby allowing the crossover 1 returns to normal, signals Unlocked switches, removal of a train to proceed without having the 6 and D47 will clear, allowing the switch padlock, or occupancy of the brakes set. In such an instance the southbound train into the station. separate crossover track circuits will motorman stops just short of the Although signal D47 is at the en set the approach signals at the stop home signal and waits. When the trance to the platform area, its con aspect. The padlock key is in the towerman pushes .the call-on button, trol has been modified so that it is case so that the switches will not be the home signal shows red-over- normally red. unlocked or moved without the case red-over-yellow. Now the motorman If a train is routed past signal 6 open, hence the release mechanism reaches out the cab window and toward D47, and the track beyond will have performed its operation. manually operates the trip release, D47 is unoccupied, the signal will To close the door of the case, the re thus clearing the tripping arm and clear allowing a train into the sta- lease lever must be returned to its

These transformers supply single-phase These rectifiers supply 16-volt d.c. for 110 volts a.c. from commercial sources control circuits of signals and switches the train may proceed. This opera tion. This was done so that a motor- normal position, which winds up the tion is usually used when switching man, routed by signal 6 over cross clockwork mechanism. There is also moves are taking place in the station over 1 reversed, would not see a pro a special emergency release key that or in case of track circuit failure. ceed aspect on D47, and also if a is under seal to be used to unlock Thus an absolute stop is provided train ran past signal 6 at stop, the the switches without operation of which prevents a train from enter motorman would not see a proceed the time release locking. The signals ing the station area if the operator aspect on D47. are not set to Stop or the timing wants it held in the approach limits. started until the time release lever Hand-Throw Switches is operated. Route Storage Route No. 2 of the Chicago sub The hand-throw switches located ways was designed and constructed Although the control machine at Hubbard street and Damen ave under the supervision of V. E. Gun- does not have route storage for gen nue operate on a hand-throw switch- lock, Commissioner and Dick Van eral moves there is one condition and-lock-mechanism. An electric Gorp, Chief Engineer of the Depart when it will store a route. With a lock on the mechanism locks each ment of Subways and Superhigh train standing by the station plat switch in the normal position only. ways. Automatic signaling and in form on the north track, Fig. 4, west One clockwork time release controls terlocking was designed and in of signal D47, a route cannot be the electric locks on all four switches, stalled under the direction of C. W. lined up for a southbound train to and it is housed in a case with indi Post, Electrical Engineer, assisted run straight into the station. Assum cating lamps. When the door of the by Walter W. Wenholz of his office, ing that crossover 1 is reversed, and case is open, the lamps are lighted as well as by C. A. Butts, Signal En for some reason the operator wants if the corresponding approach sec gineer of the Chicago Transit Au a southbound train to run straight tions of the track are unoccupied, thority. All signaling equipment was into the station past signal D47, he there being one lamp for the north furnished by the Union Switch & may set up the route by pushing track and one for the south track. A Signal Division of the Westinghouse buttons 6 and 8. The route, how handle on the clockwork release Air Brake Company, and the wire ever, will not be established because mechanism is turned which makes and cable in connection with the safe braking distance would not be the signals on approach to the cross signaling was furnished by The available from signal 6 to the train over display a stop aspect. After the Kerite Company.

182 RAILWAY SIGNALING and COMMUNICATIONS MARCH, 1952