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264 Rock Island Developes Single-Track Station- Based on Coded Track Arrangement of signals and controls make possible automatic signal protec­ tion on a very long mileage at a cost justified by increased safety protec­ tion on a line handling fast trains but a comparatively few such trains Above-Train pass­ ing single - distant si g nal l ocatio n . Right-Train a t passing-track Ioca­ rion, showing- sta­ t ion -e nt e r ­ ing signal and sta­ tion-leaving signal ON the Rocky Mountain Route of the country. Except for breaks in daily between Belleville, Kan., and Chicago, Rock Island & Pacific, be­ grade near rivers, the line rises gradu­ Goodland, Colo., 234 miles, as well as tween Chicago and Denver or Colo­ ally westward, the elevation above sea a local passenger train daily except rado Springs, there is 490 miles of level being 1,035 ft. at Omaha and Sunday between Jansen, Neb., and single track between Omaha, Neb., 5,359 ft. at Limon. F rom Limon, Rock Fairbury, 6 miles. and Limon, Colo., which is being Island trains operate over the Union equipped with an automatic block sig­ Pacific for 90 miles to Denver. The Freight Service naling system that includes several Rock Island main line extends 79 new and novel features, not only with miles from Limon to Colorado The fast through fr eight service reference to the operation and spacing Springs. During recent years the scheduled daily includes two trains in of trains, but also in the use of a new track has been improved to permit each direction 'between Omaha and and unique application of coded track higher train speeds.Lightweight high­ Limon in addition to local mixed circuits by means of which the signal­ speed passenger trains, the Rocky trains on certain subdivisions. Extra ing controls require no line wires in Mountain Rockets, are operated each trains are operated as required. Thus, the station -to-station blocks. T he ter­ way daily on fast through schedules. on some sections, as for example be­ ritory involved is shown in the accom­ In addition to a second through pas­ tween Fairbury and Goodland, the panying map, Fig. 1. senger train in each direction daily, schedules include six passenger trains Between Omaha and Limon the using standard equipment, there is and fr om four to six frei ght trains Rock Island traverses rolling prairie also a local passenger train each way totaling ten to twelve trains. On other 265 a Unique System of to-Station A utomatic Block Circuits Without Line Wires subdivisions the total may be eight to the volume of traffi c and funds avail­ ten trains daily. H eretofore there was able for signaling on this line. no automatic block signal protection on this terri tory except in a few iso­ Protection and Track Capacity lated locations for protection on of the N ew Signaling curves and over switches. and, there­ fore, the primary need was for an Thi s new signaling on the Rock automatic block system to includ e Island pro vides the same safety pro­ complete track circuits for protection tection as any other automatic signal­ again st collisions as well as to check ing, including protection from colli­ for broken rails and the position of sions, broken rails and misplaced switches in the entire terr itory. On switches. The installation includes account of the extended mileage, 490 separate automatic blocks through the miles, between Omaha and Limon, limits of the stations. the same as in the character of the line, and the com­ conventional signaling. F or example paratively light volume of traffic, only at station A in Fig. 2, signal 9 is the a limited expenditur e could be author­ westwa rd station-entering signal, and ized for the desired signal protection. signal 10 is the eastward station-en­ In this instance necessity was the tering signal. In orde r to give an en­ mother of invention. The Rock Island gineman advance inf ormation con­ signal engineer and his staff planned a cern ing the aspect displayed by a sta­ continuous track circuit controlled tion-e ntering signal, there is a distan t system with blocks extending from signal located at full braking distance station to station. plus medium-speed braking distance f rom each station-entering signal. For No Intermediate Blocks example in Fig. 2, signals 7 and 12 are the distant signals for station -enter ing East of F airbury no intermediate signals 9 and 10, respectively, and sig­ automatic blocks as such ar e provided nals 6 and 1 are the distan ce signals to permit trains to follow one another for station-enterting signals 4 and 3, in a station-to-station block. Vi est of respectively. An important point is Fairbury, however, the signal system that signals such as 1, 6, 7 and 12 are has been further developed and ex­ merely distant signals and they are not tended to prov ide addi tional signals in located or controlled as intermediate the center of certain station-to- stati on automatic signals. Single-distant signal location show­ blocks in excess of eight miles in ord er ing instrument case and battery bo x to permit trains to follow each other. Station-to-Station Block Thi s featu re is accomplished without Is Something Di fferent the use of line wires, and the signal project, when an eastbound tr ain de­ layout is similar to that at a passing In this Rock Island project the sta­ parts from station A, the eastward tr ack locat ion, but minu s the passing tion-leaving signals and their controls station-leaving signal 8 at this siding track. are different from conventional prac­ will continue to display the Stop as­ Furthermore, the Rock I sland sig­ tice in that the block is from siding to pect to hold a following eastward nal staff devised a new and novel siding, so that following trains are us­ tra in until the leading train has passed scheme of using coded track circuits ually spaced the full station-to-station beyond station B or has entered the to cont rol single-track autom atic block distance rather than being spaced by siding at that stati on. signaling without line control circuits inter mediate automatic signals, with On this territory of the Rock Is­ in the station-to-stat ion blocks. As the excep tion of certain instances west land, following tr ains of the same compared with conventional signaling of Fairb ury, mentioned heretofore, class and speed ar e not ord inari ly op­ the use of station-to-station blocks re­ where intermediates have been in­ erated very close together, and, there­ duced the number of signals required, stalled in station-to-station blocks fore, the spacing from stat ion to sta­ and the new circuit scheme eliminated longer than eight miles to allow for tion does not cause tr ain delays on this line wires and pole line work so that following train movements. Ref erring score. Where a fr eight train is on a the cost of the installation is consid­ to F ig. 2, which illustrates a station­ siding waiting for a passenger train ered to be in proper relationship with to-station block in the Rock I sland of the same direction to pass, the 266 RAILWA Y SI GNALING Apr il, 1946 freight will have to wait at station A, With an eastbound train passing from additi on the yellow is an Approach for example, until the passenger train station A 'to station B, signal 12 re­ aspect indicating that signal 9 is dis­ goes beyond station B. O n account of main s at Stop until the train has playing red. Also signal 7 displays the few instances of thi s nature due passed signal 8, af ter which signal green to indicate that signal 9 is dis­ to the compa ratively small total num­ 10 displays Approach, and signal 12 playing yellow or green, and that the ber of trains, and because the high clears to allow a second train to fol­ tr ack is unoccupied between signal 7 speed of passenger trains reduces the low. Signal 8 will not clear until the and signal 11. time to pass beyond the next station, first tr ain is by signal 4 and signal 6 the delays due to the station-to-statio n is displaying Approach. Impulses Feed Both Directions, Ar e blocks are few and of short duration. Co-ordinated to Prevent Interfer­ These delays are recognized as neces­ Aspects Displayed ence, but Are Not Interdependent sar y in the system based on the sta­ tion-to-stat ion block, which in turn In F ig. 2, station-leaving signals In a station-to-station block, as for was accepted in order to reduce the such as signal 8 at station A and signal example between signal 8 at the sta­ costs to be in conformity with funds 5 at station B are absolute signals to tion A and signal 5 at station B, the which could be justified and author­ which R ule 292 app lies. Such signals signals are controlled by a new and ized. Based on observa tions since long are normal-clear signals. In view of unique adaptation of tr ack circuits, sections of the signaling system have the fact that these are station-to-sta­ without the use of line circuits. T he been placed in service, the trains leave tion signals, they display only two as­ commonly accepted term coded tr ack stations on green aspects, thus accel- pects, red for Stop and green for Pro- circuits does not exac tly apply to this - -- --- -- r-'-KAN'-S AS'-'- COLORADO I i~l l ToDenverts> t:: 0, c ......

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