IRSE Examination 2015 Module 2 Signalling the Layout. Typical Answer (2) Main Line Practice (Layout 1)

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1 IRSE Examination 2015 Module 2 Signalling the Layout Typical Answer (2) Main Line Practice (Layout 1) This candidate provided a comprehensive solution to the requirements specified Question 1 1a Braking distance calculations are correct; separate calculations being shown at 100km/h for freight and passenger traffic. 1b Headway calculations are correct for three and four aspect signalling. The point is made that whilst three aspect signalling would theoretically satisfy the headway requirement for non-stopping trains, with stopping trains, four aspect wold be more suitable. In the layout, four aspect signalling has been provided throughout on the main line. 1c A less than adequate solution. The distance that the freight train has to travel is miscalculated and the candidate assumes that it is accelerating for the whole distance, thereby exceeding the permitted speed over the junction at D. Question 2 General The method of working of the level crossing at C is not stated. The method used for propelling freight trains into the yard at F is not defined. (This could be by shunter/driver radio communication, or by the provision of set-back signals controlled by the shunter.) The method of working on the branch between F (exclusive) and H is not stated. Down signals The approach from A should be signalled back to the first caution for the protecting signal (1) at B. On the branch, the A facility shown at signal 101 is superfluous. Signal 500 at the exit from freight terminal F does not need a green aspect, as freight trains will only run clear of 11016B points. There should be a distant board at the approach to station H. Up signals There should be a distant signal in rear of signal 104 Signal 18 at the exit from the up sidings at C should have a subsidiary aspect Shunt signals 500 & 501 should require a proceed aspect on signal 18. Subsidiary/Shunt signals There is no provision for permissive working on the goods lines. Set-back shunt signals at either end of station C should be shown. There is no justification for the preset shunt signal (602) on the branch between D and F. Route Boxes Incomplete. Numbering Ref SA101 Page 1 of 2

2 Satisfactory Overlaps ROLs should be shown only where required by the operating requirements. An ROL is shown on the down Goods line at signal 15 with the previous signal 9 plated as automatic. This would only work if signal 9 is approach controlled for all movements, but this is not stated in a route box. Signalling symbols Generally satisfactory Question 3 At D, the Up Branch to Up Slow facers (1013) are correctly shown to trap against the Up Main. They could have been combined with 1012 as a crossover. The Up Branch siding traps are not numbered. In the Freight Terminal, hand-worked points are incorrectly shown with normal lies and numbered in the same sequence as points intended to be power worked. Question 4 Train detection on the Branch is indeterminate beyond HQ ; all that is needed for the one train working portion of branch beyond the signalled area and station H is a single axle counter head. It would be economical to combine CP/CQ and HD/HE into single track sections (no overlap requirement at CP/CQ). Ref SA101 Page 2 of 2

3 IRSE Exam 2016: Module 2 Sample Answer Question 1a Determine the minimum signalling braking distances for the main and branch lines shown on layout 1. Main line: Non-stop pass train: Main line: Stopping pass: Ref SA101 Page 1 of 4

4 Main line / Branch line freight: Branch pass: Question 1b Determine the best theoretical headway for both 3 and 4 aspect signalling between A and E at uniform minimum signal spacing and a non-stop train speed of 180km/h. Explain how the results of the headway calculations determine your choice of signalling system. 3 Aspect Ref SA101 Page 2 of 4

5 4 Aspect With a potential of 21 trains per hour, there needs to be a headway time of: 60 x 60 = 171 seconds minimum 21 Therefore both 3 and 4 aspect in theory will achieve this headway. However, with acceleration/deceleration time and also station dwell time, 4 aspect would be more suitable to achieve the headway in reality. Ref SA101 Page 3 of 4

6 Question 1c Immediately following the passage of a train from A to E, a freight train standing at the exit signal of the Down Goods line at C is given a proceed aspect to run onto the Up and Down branch line at D. The freight train starts to move after a delay of 20 seconds and accelerates to 40km/h over the junction at D. Determine, graphically or by calculation, the minimum time that can elapse before the freight train clears the junction to enable proceed aspects to be given for an Up train to run from E to A. State all assumptions you make. Freight depart at 3400m. Assume clearance point after junct is at 2600m with an IBJ. Train length = 400m. Therefore total distance traveled = = 1400m. t = 74 seconds to clear junction = 94 seconds before next route can be set for next train Assume TORR and ARS Ref SA101 Page 4 of 4

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