IRSE. Institution of Railway Signal Engineers. IRSE Professional Examination MODEL ANSWERS (from 1997)

IRSE Institution of Railway Signal Engineers IRSE Professional Examination MODEL ANSWERS (from 1997)

IRSE Profession Examination Model Answers Examination Year Module Page 1997 Module 1 Risk Assessment 3 1997 Module 2 Aspect Sequence Chart 5 1997 Module 5 Level Crossings 7 1998 Module 1 System Life-cycle and Human Error 10 1998 Module 2 Signalling the Layout - Mainline 13 1998 Module 2 Aspect Sequence Chart 21 1999 Module 5 Question 1 22 1999 Module 2 Aspect Sequence Chart Layout 3 29 1999 Module 2 Signalling the Layout Layout 1 30 1999 Module 3 Signalling Principles 40 2001 Module 2 Signalling the Layout Layout 1 32 2005 Module 3 Signalling Principles 42 2006 Module 1 Question 5 45 2006 Module 3 Question 5 49 2005 Module 2 Layout 1 51 2007 Module 3 Question 8 67 2007 Module 4 All questions 70 2007 Module 6 All questions 89 2008 Module 2 Main Line Practice 112

154 IRSE Examination 1997 Module 1 - Question 2 - Model Answer QUESTION (note - two questions to be done in one hour). Define Risk Assessment. Discuss the degree of quantification that may be appropriate for railway activities and give two examples. How should a railway organisation determine whether a particular level of risk is acceptable? ANSWER (spelling corrected and some unnecessary capitalization suppressed) Risk assessment. This is a method of assessing risk and reducing it appropriately. Risk: Is the probability of an unwanted evenvhazard occurring and the severity of its consequences. Risk = Probability of hazard X severity of consequence. Risk can be expressed quantitatively or qualitatively. Qualitatively is like expressing risk as unacceptable, broadly acceptable, tolerable or negligible. Quantifying Risk is a means of expressing the risk criticality numerically. The are various methods for doing this, one of which is Quantified Risk Assessment (QRA). QRA is a numerical method of assessing risk and reducing it. FMECA is a method of quantifying risk. FMECA - fault mode effects and criticality analysis. Two examples are shown below For fig 2 Risk 8-A = Prob x Consequence C-A = 1 x 1 x 0.1 x 8 = 0.8 A-8 = 1 x 1 x 0.1 x 10 = 1 =1.8 From the examples shown the risk in fig 2's layout (1.8) is a lot bigger than fig 1 's layout (0.6) assuming the driver ignoring the AWS system which will be in place on the train. A probability of which was given 0.1 A railway will determine whether a risk acceptable depending on whether it is all right unacceptable regardless of whether any mitigation is carried out 0 the system or not and so it will have to be rejected. It might be acceptable if certain disaster recovery systems are in place which might reduce the risk. A risk will be accepted if it is as low as reasonably practicable. If the economics of the risk is too expensive to reduce then it might be accepted if procedures or systems in place to compensate for this risk e.g. 24 hours emergency aid on stand by A railway organisation will determine if a risk is within this areas and if acceptable by risk analysis techniques mentioned above FMECA and QRA. The level of ALARP risks are shown below Not Acceptable Acceptable lifeconomic alternative too high) Figure 1 Figure 2 AE Fig 1 and 2 are two examples of how to get from 8 to A. 80th are assessed quantitatively as follows Train density 80th Roads Consequences Head on A-8 = 1 trainlhr A-C = 1 train/hr Converging 8 Crossover 6 Probability of a signal passing a SPAD - signal passed at danger = 0.1 For fig 1 Risk 8-A = Prob x Consequence A-C = 1 x 1 x 0.1 x 6 = 0.6. 10 c c Rating Broadly Acceptable COMMENTARY In response to comments made about previous papers, a time of five minutes for candidates to read the paper before starting is allowed and the questions were made shorter. The examiners are looking for a professional answer which is one which communicates clearly an understanding of the subject. This candidate's answer was clear even though the English was poor. Correct prose is expected rather than notes, but lists can help to show the structure of an answer and earn marks without unnecessary words. With time allowed to read the paper before starting candidates should make time to read through their answers and correct minor errors and this answer would have benefitted from such correction. The answer does contain the key elements sought: a definition of risk as probability of occurrence times severity of consequence; some (poor) discussion regarding degree of quantification; two examples; and an answer (of sorts) about what level of risk may be acceptable. The strength of this answer lies in it being complete. It also demonstrates that the candidate has understood how to

IRSE EXAMINATION 1997 155 apply risk assessment. The weaknesses which lost marks are unhelpful additions and poor development of ideas. In the opening there is considerable repetition as if the candidate was struggling to get started. Risk Assessment is actually about assessing risks in a consistent way to enable rational comparison. Thus the mention of "reducing" risk is out of place. It is often the case that risk assessment can enable mitigation measures of different cost to be evaluated and thus the most cost-effective risk reduction strategy can be selected, but the risk assessment itself is an analysis of a situation as defined. Later the candidate mentions FMECAs (with the "f" wrongly defined as "fault" when it should be "failure") and states that they are a method of quantifying risk. This is not true because a failure mode effects and criticality analysis is used to show the effect of one failure at a time whereas fault trees can show the effect of multiple and dormant failures. Risk assessment is a measure of the risk from all eventualities from operating the defined system. Thus the degree of quantification necessary is that necessary to ensure that risks are correctly ranked and in proportion to each other when being compared. The initial assumptions were clear. Throughout the examples there is an implied assumption that the signalling provides flank protection by points and this should have been stated explicitly. The use of "ALARP" as the answer regarding acceptable risk is only just adequate and some discussion of what constitutes "practicable" is necessary to complete the answer. This should relate to the stated safety target in the railway's safety case which may be in maximum number of fatalities or injuries from a given cause in a given period or may be expressed in terms of cost to be spent for each fatality/injury avoided. This answer has many obvious limitations but was awarded a credit mark for conveying the essential elements. Some candidates used other definitions of risk as used by differing railway administrations, often including the use of time to detect failures, and the examiners accepted any coherent answer which showed the basic comprehension of risk assessment. Candidates should be careful of their descriptions of ALARP particularly in the "acceptable" region. Some candidates lost marks through a tendency to assign risks that are "obviously minor" to this category whereas it is essential to be very thorough in the assessment if sufficient robust proof is to be recorded that the risk is indeed that small, and also it is necessary to ensure that management measures are in place to ensure that these risks remain small. Answers to this question had a wide range of marks showing that, while some where very good, there is still some confusion regarding the basic techniques of modern safety management systems. Candidates are expected to choose two questions from seven and thus select subjects of which they are familiar and can demonstrate their professional judgement. IRSE Examination 1997 Module 2 - Question 5 - lypical Answer Commentary This solution to the aspect sequence question gained high marks. The layout adopted was not the most elegant because of the many right angled lines needed, but it was nevertheless well laid out and neatly drawn. The candidate spotted the "deliberate mistake" in that 107 signal is incapable of showing a double yellow aspect, given the approach control conditions for the junction beyond 111. (The profile of 107 is correctly shown with a four aspect head to avoid giving drivers the wrong impression of intermixing 3 and 4 aspect signals.) Higher aspects were brought back from 108 to 112(2); although not incorrect, its use in normal working appears unlikely. However, the higher aspects from 108 to 122 would serve a useful purpose in allowing a branch train unrestricted access to the down main platform. This feature could have been enhanced further if the yellow aspect on 122 had been taken back to 126(2), after its approach control conditions had been satisfied. (The candidate incorrectly applied approach control to DD track occupied on 122(1), although not called for in the route box.) Them were other omissions in regard to interpretation of the approach control conditions given in the route boxes to the aspect sequence chart; these concerned: 126(2) CD occ. should have been CE occ. 122(2) DD occ. for t1 should have been DD occ. 111 (1) BH occ. should have been (BG or BH). The overlaps were correctly shown, including the reduced overlap beyond 111. (The "Overrun" shown beyond 117 signal has no significance in aspect sequence terms.) This solution was considered all the more creditable since the candidate answered the other questions in this module on the "rapid transit" layout, using two aspect signalling! NOTE: The candidates answer has been re-traced using CAD techniques as an aid to its reproduction in the proceedings.

ASPECT SE~UENCE CHART (DOWN DIRECTION). W THIS IS AN ERROR: V I1I MUST ALREADY BE SHOWING Y+POS I (AS CANNOT SHOW Y ALONE). THEREFORE B H OCC TO aear J.I. IS ONL Y ONE METHOD. ALSO PROVIDE BD OCC FUNCTION. - - - SHOWN DomD CIJ = SIGNAL No'X' OIL = OVERLAP * NOT OIL AS NO MO'v'E I1 = TIME DELA Y. TRAIN ALMOST READING UP TO THIS SIGNAL AT A STAND AT SIGNAL. Iilll OVER-RUN t R ~ t ~ [IQZJ 0 L [ill II@. [@] OIL ~---- R ' [ "DC"roll [!TIll R ~ ~ [j BDOCC.", Y : all [ I I ~ R Q!!, Y I yy T Y,-- m _mu_m, Y 'l)\' I I G G yy C G L----BJ~~(~----yy-);f > G,0;, I G I: G,-- --------- ---------- yy----- I L G.---' G [ill] R G OIL I -" 01 Cl) UP DIRECTION. ~IL NB SIGNAL 1r.~BR O~IITfED [@] G -l ~ 1 ~ [@J R Y ~L rl j loll R Y yy Aspect Sequence Charl for Layoul 3. 1997 Examlnalion Candidales Answer. G NOT SURE HOW THIS IS SHOWN li' 'DOWN BAY' IL I -<'J---II-l-I--+-I_ O ~. I OiL r9ll R Y ~ If ~;' CDQCr r G =:J I I ~ ~ ~ loll R Y yy Y +POS4 AGOCC yy ~ G yy.,os< I I G ---.J L-~========== ~.NlS' L ~=1 I I [ill) [ill] :;; ~ ~ ;:: z ~ CS z ;;; <0... li\.":1'

-- --. - -. Institution of Railway Signal Engineers 1997 Examination. Layout 3. For use with Modules 2,3 & 6. - \, p' - 103 I - 104 F: 9 +asm 4 r 5 m j l t 915m - I F-E-a& b 88.,- 2 DownMam4 df* f--~owh Main- +UD Mainf ~ l l +Up Main TrakCLcuilhck +....--- - %i a 1 4 R J 108BR - - b G&&al Brea Qnlv 1.3600 -._- I 20 x 7.2 ins -

IRSE EXAM 1997 Model Answer for Circulation to Candidates Module 5 Question 10 The question: A level crossing, normally open to road traffic, is equipped with four barriers and supervised by closed circuit television. Yellow and flashing red road signals are provided, together with red lamps on the barrier arms and audible warnings for pedestrians. Describe the main features of a mechanism that could be used to operate the barriers, using electricity as the source of power. Describe a suitable sequence for operation of the equipment concerned, when the crossing is to be closed to road traffic and when it is reopened after a train has passed. Describe a method for ensuring that the operator looks at the television picture every time (s )he closes the crossing, before authorising train movements over it. The candidate's answer: Each barrier could be operated by an electro-hydraulic ram pack housed inside a weather proof pedestal shown in cross section below:- In the raised position, the ram is extended & held by pressure within the hydraulic circuit.when required to lower, external contacts cut the supply to an electrically operated valve inside the power pack, causing the valve to open & the fluid under pressure to run back into a reservoir as the barrier lowers. This takes approx 6-8 seconds, the [mal 5 or so being damped by an internal flow control valve as the boom comes to rest in the horizontal position. To raise the barrier, fluid is pumped in the opposite direction by an electric pump that cuts off at about 83 from horizontal and then held there by the now closed valves. A typical supply voltage would be 24V, backed up by lead-acid or NIFE cells to cover supply failures but also to prevent the voltage dipping because of the high demand during the raise cycle.

Other features of the pedestal mechanism include (I) a hand pump for use during failures (ii) counterbalance weights to give the necessary "out of balance" force at the boom tip. The number of weights is determined by the boom length. (iii) a circuit controller for use in conjunction with external circuitry i.e. Detecting the barrier has fully raised (usually 81-90 ) Detecting the barrier has fully lowered (usually 0 _4 ) Controlling the drive of the motor (usually 0 _83 ) Controlling the red flashing road lights during raising such that they extinguish at approx 45 The normal sequence of events when closing the crossing to road traffic would be as fiollows:- (I) Operator at control centre / signalbox presses "Lower" button on control unit for crossing (built into panel or free standing pedestal), having ensured that there are no obstructions on the crossing by visual check out of the window (manned barriers) or via a CCTV screen. ( ii) Yellow road lights illuminate on all light units for approx 3 seconds (iii) Red flashing road lights illuminate on all light units (more than one light failing to flash on any unit resulting in a flashing indication on the control pedestal) (iv) Approx 4 seconds later, the nearside booms start to lower and boom lights illuminate. Once they have reached the fully lowered position, the offside booms start to lower- (v) (vi) Once all the barriers are fully lowered, the operator receives an indication to this effect. This means that the protecting signals reading over the crossing can now be cleared for a train. Once the train has passed, & the protecting signals are at red and not approach locked, the operator can either raise the barriers using the raise button or, if AUTO RAISE control is selected, this will happen as soon as a positive sequence of track circuits between the signals and the far end of the crossing have been occupied & cleared. The remaining part of the sequence would be:- (I) All 4 booms raise simultaneously (ii) The red flashing road lights extinguish at about 45 (iii) Boom lights extinguish at 81 To ensure that the operator is checking the crossing on the CCTV monitor before clearing signals, repeat relay of the button that brings the picture on must be proved energised which in turn is used in the control of a stick relay that follows a "crossing clear" button on the console that effectively says "operator has used CCTV camera & confirmed crossing clear".

This "crossing clear" stick relay must be energised before any protecting signal can be cleared to a proceed aspect. Examiner's Comments The candidate has given a very full answer which attracted high marks. He has answered all parts of the question. The hand-written answer occupies 4 pages, and the candidate must have known the subject well to complete the answer in half an hour. First, here is a description of what was intended by each part of the question. The scope of the subject is large, so the question concentrates on certain areas only. The question was not intended to be interpreted as "Write all you know about the operation oflevel crossings supervised by CCTV". The first paragraph is an introduction, not itselfrequiring an answer. The second paragraph begins "Describe the main features of a mechanism... ". In the candidate's answer, the mechanism is the ram, valves, power pack, and the 3 "other features". The third paragraph of the question begins, "Describe a suitable sequence... ". It was expected that the candidate would,describe the broad principles, and he has done that. The "equipment concerned" is that mentioned in the second paragraph of the question. The candidate's sequence has related operation of this mechanism to that of the other equipment mentioned in the first paragraph of the question. The operator's actions were not included in this part of the question, but the candidate has given several; this is one reason why his answer is relatively long. In the first 3 paragraphs of the question, the interface with railway signals is not mentioned. This subject is introduced only in the last paragraph, to ensure that the answer covers this subject.. In his answer, the candidate has shown that he understands the problem and could specify in principle a method for dealing with it. In all parts of the question, fully detailed circuit requirements were not expected, as they could not be described within the time allowed. The sketch of the barrier arrangement has been clearly drawn. Audible warnings are mentioned in the question, but have not been included in the description of the sequence of operation. Prepared by: K.Donnelly 01812369420 23rd February 1999

Commentary Answer IRSE Examination 1998 Module 1 Question 7 Railway signalling and telecommunications systems rely on human actions to ensure that they achieve safety at all stages of the system's life. What are the main stages of a system's life-cycle and what management methods are appropriate at each stage to prevent human error affecting safety? Candidate's answer The main stages of a system's life-cycle are : 1 Concept 2 Design 3 Installation 4 Testing and Commissioning 5 Routine Maintenance 6 EmergencyIFailure Maintenance 7 Mid-life modificationlupgrade 8 Decommissioning 9 Removal and disposal Management methods to achieve a successful project should start at a recruitment level by getting the right people involved from a draughtsman up to the tester in Charge, Proj ect manager etc. All staff should be fully licensed to the required standard. The above statements apply to all stages, however, there are other methods and practices which relate mainly to one or more particular tasks: 1 Although maintenance is some way off for the new system it must be designed with maintenance in mind, i.e. Access to Equipment, checking the time between failures so that equipment expected to fail more is much easier to access. 2 Ensuring a "Safe System of Work" is established for the installation stage and that existing systems are functioning correctly at the end of each shift. 3 If stage working is required for bringing in the new system a comprehensive "Testing and Commissioning Plan" should be produced and approved. 4 The new system should have been added to the Asset register so that a maintenance contract issued at the start of operations. 5 Before any modifications or mid-life upgrades are designed or installed a correlation exercise should be carried out to ensure no 'unauthorised' modifications have been made. 6 At the end of the system's life care should be taken on the disposal of the old assets. LUL still uses lead covered cables and lead-acid batteries. These items should not just be thrown away but disposed of in an appropriate manner. The use of asbestos and other harmful products should also be treated with care. \0

The main bottom line of avoiding human error affecting safety are: 1 Training 2 Licensing 3 Supervision 4 Safe system of work. Commentary This question was not answered well by any candidate who chose to answer this question as one of the two to be selected from ten questions set. This choice is provided to ensure that candidates can choose subjects about which they can provide a professional standard of answer. The above was the best answer given to this question. The reasons why it scored over a pass mark is its clarity, the use of lists to show scope, and the way that it does have some response to the main parts of the question. A good answer may have made reference to the life-cycle described in the European Norm 50126 before stating the important steps to be addressed.. This candidate gave nine steps which concern a railway organisation but it omits the stages of the supply chain where safety could also be affected. It should be remembered that signalling systems are complex and interlockings have many potential operating states when all the input permutations, sequences and timings are considered, so that it is not practical to test for all possible faults once it is assembled as a whole, so safety depends on the care taken at each step. It is for this reason that component procurement, system manufacture, factory test, transport and storage all need to be managed to prevent human error leading to danger. Even leaving a cable cut with its ends unprotected can lead to moisture entering the cable and causing deterioration of insulation in some cables. More could have been said about the standards to be used in an organisation to ensure that quality work is achieved, starting with ISO 9000 type quality systems and then introducing requirements for construction and design management. An organisation structure affects the achievement of safety as has been commented on in recommendations in reports into recent accidents. Safety standards should be set and an organisation established accords responsibilities to suitable staff working where there is independent monitoring and reporting of safety achievements. The answer given does say that recruitment is important, but does not explain the techniques that might be used at an interview to establish an applicants dependability. The answer states that "all staff should be fully licensed to the required standard" without noting that licences categories are not established for every position where human error can affect safety, nor stating what any "required standards" might be. At the design stage account should be taken not only of maintenance but of all stages of a system's life. Examples should be given of how designs can be developed to reveal potentially dangerous conditions arising from human error, such as the provision of earth leakage detection on some circuits. The design processes and the procedures for checking and authorising work are important. There is no explanation of how a human factors study may assist to ensure that work is organised in a manner where error incidence is minimised, for example through task analysis and consideration of performance shaping factors, or assessment of ergonomics. Wiring schedules can be read with greater accuracy if the rows and columns are in groups of five rather than in one huge grid. The use of different colours for copies of drawings can be used to distinauish the life-cycle step to which they apply. Pincoding connectors and relays prevents wtong assembly. Prevention of damage during l\

maintenance is facilitated by keeping tools and equipment calibrated and in good order. There are other weak parts to this answer in that it uses terms like "approved" and "appropriate manner" without stating what constitutes approval criteria and what manner is appropriate. Recent IRSE papers and publications on human factors give other useful examples which would have enabled this answer to be developed to a more professional standard. Another question that was not answered well was one on cross-acceptance of signalling and telecommunications systems used by one railway, for safety critical application on another. A number of candidates stated that, because much equipment today is processor based, it is merely a question of putting the new railway's requirements into the software. This is a very dangerous misconception because different railways use different system states as safe states - some fail to a safe state (signal to red) while others fail safely by not changing state under failure (a block instrument). Thus the safety principles of one railway may well require particular operations to be effected to achieve one safe state, when the equipment is designed (and safety assured) to fail to a different state which suits the differing safety principles for which it was originally developed. These problems are rarely revealed by testing because testing is usually done on fault-free equipment. Again, the IRSE provides a publication on cross acceptance which would have given many examples to help answer this question. \L-

I IRSE Protessional Examination Model Answer Module 2: Signalling the Layout 1998 The following is a "model answer" for educational purposes only. It is not anticipated that the candidate would be able to complete this paper to the same level of detail under exam conditions. However, the closer the resemblance, the higher the pass mark awarded to the candidate. 13

rt...... Cl>... o H> Institution of Railway Signal Engineers 1998 Examination. Layout 3. For use with Modules 2,3 & 6. Signal 106 Route Class 1 Main 2 Main Destination Asp Indr Up Branch Main Pos2 Uo Main Main Pos 1 Approach BH Occ BH Occ GJ - N...... DOWN MAIN 1100 Km'h DOWN MAIN DOWN MAIN 1 00 Km'h 1 80 Km'h 80 Km'h I 65 Km'h CROSSOVER 202 35Km'h j.e-915 915- -915 915---7k-915 915---7k- 521 1m 1rol 1~1 1W ~~~~ 521-~ 580-~. W BA I W BB I W BC I BD. BE BF 202B ~ BG BH..:LH- Track Circuit Block BRANCH 1100 Km'h Track CircuH Block 18tOL i8tbl 18tOL Down Main ~ 18tOL.? r--.,,-.,. A"l"-. +-Down Main ~ DA Braking composite curve for passenger trains. All dimensions in metres. AWS not shown. Loco hauled train length. Multiple unit train length. 200m 100m Scale: Central area only 1 :3600 1830L..- CA ~ CB 201 CD ~ I l' +- Up Main ~ +- Up Main ~ ~ 102 i'e-600 k-l000 I ~ ~. 1000---7k- 580 600 71<: 402 I 117 I. 121 80 Km'h TURNOUT 201 80 Km'h ~~ I 65 Km'h UP MAIN W DB I DC W I DD DOWN BRANCH +- Up Branch Down ~ 100 kmh I 80 kmh Overlap Symbols OL 1- Signalpost Signs ~Automatic ~ Distant (No Red) DOWN BRANCH 1 80 Km'h I 65 Km'h UP BRANCH 1 100 Km'h I 80 Km'h Signal 121 Route Class Destination 1 Main Down Main 2 Main Uo Main Asp Indr Approach Main Pos 1 DCOcc Main Signal 104 Route Class Destination 1 Main Uo Branch 2 Main Uo Main Asp Indr Main Pos 1 Main 111

)proach oh Occ,H Occ Signal 301 Route Class Destination 1 Shunt Down Main 2 Shunt Uo Main Signal 302 Route Class Destination 1 Shunt Uo Main 2 Shunt Down Main 3 Shunt Sidina Asp Indr Shun D Shun U Asp Indr Shun U Shun D Shun S J I Signal 113 Route Class Destination 1 Main Platform 1 1 Call On Platform 1 Occ 2 Main Platform 2 2 Call On Platform 2 Occ 3 Main Platform 3 3 Call On Platform 3 Occ 4 Main Platform 4 4 Call On Platform 4 Occ Asp Main Sub Main Sub Main Sub Main Sub Indr Approach Presets 1 BKBLOce 3031 Min 1 BLOce 303 1 2 303 2 Min2 BL Oce 303 2 3 3051 Min3 BL Oce 3051 4 BKBL Oce 3052 Min 4 BL Oce 305(2) I Signal 303 Route Class Destination Asp Indr 1 Shunt Plartorm 1 Shunt 1 I 2 Shunt Plartorm 2 Shunt 2! Signal 305 Route Class Destination Asp Indr 1 Shunt Platform 3 Shun 3 2 Shunt Platform 4 Shun 4 I V5.1517!98' 521-~393 580-~ Siding Signalbox I~I Ground Frame d Release Lever GF2 I I. AA Released by 208 PI tf ] I FPLs Normally In a orm 1 (110m) BL 113 FPLGF4 ~ ~ ~ CG =t= 200 402 560 Signal 125 Route Class Destination Asp 1 Main Plartorm 1 Main 1 Call On Plartorm 1 Occ Sub 2 Main Plartorm2 Main 2 Call On Plartorm 2 Occ Sub 3 Main Plartorm 3 Main 3 Call On Platform 3 Oce Sub 4 Main Plartorm4 Main 4 Call On Platform 4 Oce Sub 125 200 65 Km'h 25 Km'h ALL LINES Indr Approach Presets 1 CFCG Occ Min 1 CGOcc 2 Min2 CGOcc 3031 3031 303 2 303 2 3 Min3 CGOcc 4 CFCG Occ Min 4 CGOcc 1OfoL Signal 114, 116 3051 Route Class Destination 3051 1 Main Up Main 3052 2 Main Down Main 305(2) 3 Shunt Sidina Asp Indr Presets Main U 302(1) Main D 302(2) Sub 302(3) 560=, CL Platform 3 (30Om) FPL GFl Platform 4 (11 Om) ====, Signal 118, 122 Route Class Destination Asp Indr 1 Main Up Main Main U 2 Main Down Main Main D 3 Shunt Siding Sub Presets 302(2) 302(3)

Institution of Railway Signal Engineers 1998 Examination. Module 2. Layout 1. 1 Candidate Number I I Train lengths Main line passenger Branch line passenger Freight 200m 100m 200m 400m Acceleration Rate All trains Braking Rate All trains - Permitted Speed Passenger (Main & Branch lines) # 100 kmlh.. Freight (Main & Branch lines) # 100 kmlh Main line turnouts at Junction D and F 80 kmlh All other running line turnouts 40 kmlh # Except between tunnel mouths at E. 40 kmlh Required Headway Main lines: following stopping at 80kmlh 3 min Normal Maximum Contracted Paths Express Passenger Through Main Lines (A to H) 1 per hour each way Terminating from South Lines (E to G) 4 per day each way 1 Semi Fast Passr Through North to South Lines (C to G) 1 per hour each way I I I Local Passenger Terminating from Main Lines (A to E) 2 per hour each way Terminating from North Lines (C to E) 2 per hour each way Freight Working Scale 1 :2000 All Lines Maximum Reversing at E (G to H) 1 per hour each way 1 per day each way All passenger trains stop at Station E. Semi fasts cross at E & connect with southbound express A to H. Local passenger trains are stabled and serviced at the Carriage Depot. I \ I Gradients Level except in flyunder which is average level Method of Working 1. The method of block working on the main lines and branch lines should be shown. 2. The method of working to and from the carriage depot should be shown. 3. Permissive working is permitted for normal working on the Goods Lines and emergency working in the platforms. 1 1 pie as^ read the above inforrnali~n carefuiiy v2. I 6/7/98 1 I I I I 1 I 1 i I 1 I L I I 1 I I 1 tile 1 of 11 (1,l)

162 Up Main --+ Track Circuit Block *ta~-~~~) -.Down Main,- i a 4-, Down Main EA I, t t **: : b - 0raking Distance at 100km/h=Bd V=lnitial Velocity =I OOkm/hour. A=Deceleration Rate=O.Sm/s/s 100krn/h= 100000mf3600s=27.8mlsecond Bi Braking Bd=(VxV/2A)=(27.8~27.8)/{2~0.5)=773m. Carriage Depot 4y Arrival Line Headway Distance=Hd Sd=Sighting Distance= t83m. Td=Length of longest train=400m. Bd=Braking Distance=773m. Qd=Overlap Distance=l83m. Hd at 1 OOkmlh=Sd+TdtBd+Od=l539rn Ht= Headway time= Hd127.8=55.Wconds. TRAIN PASSING THROUGH STATION at 40krnlh 4Okm/h=40000m13600s=11.I l m/second Braking Bd=(VxVI2A)=(ll.I 1 xl 1.I 1)/(2~0.5)=123.4m. ; Hd at 100kmlh=183+400+123.4+183=889m Ht=Headway time=88911 I. 1 t -8Oseconds. All headways well within requirements of 3 minutes. Will allow station dwell time of 100seconds. 1 :2000 Dimensions in Metres ; id L L Stop and Await Instmctions ~elephoie Sialbox to Shunter,* *a- a- Departure Line ->,*.+ a., a#* I tile 2 of 11 (2,l) tile 3 of Ib

Up Main -+ T Down Main - t i 8 3

Junction D Main Running Turnouts 80 kmlh Shunt 313 - @ 85 Approach. 313 @$. L \I DC A, DD -a- V - I, 224 I North ~unnel (1 Free Yellow tof tiwergence with Fbiihmg aspects in Ihe rear. 8eps lo Green when EF &pied II next signal slmwing proceed Conlmll~lmm Red by EF or ED ocwpied I ikhing sequence lails. B 164 -++ - T AB Up North- 183 --tg Traclc Circuit Block +tm HA - 4- Down North I 4' I

Sped is 40 knvl lor ay mvle5. Appoach control onb required for Warning. Call On and Bay plafforms, form 1 73). 846 Tv lo R. - Pla!twm 4 I Goods 154 -a -.-.- ----------------m :=--- 85 4ppcoach Rekase Iu Warner and Call On k p ~ s + -. ""-'--" ------*-.----* T a0 -f DF t 569 to Bay Pladorm 2(Approach Conltol) 569 to Bay Platfon3 (Approach Cmtrol) Vl 1 -_----- m*.------ North Tunnel (1 97171) I I Middle Tunnel (210 m) 151 " Requires EH Occ Unless 153 Cfl (BD-773). Y to A. 382 487 E Aou$ lndn 3wn North A

Main 149 Roll9 Cbu kiw lndn Destinatun warn A Hsln YKi Oorm~dn #2 Mn pelerred route. #I. Prelecred route. Overgp no1 Perrnmed t AG 149-EPE-138 A - P Platform 2 Platform 3 - FOLFor131 +Up Main- +- Down Main EM FG De5tiit1on Platform 1 Phtform 2 Flatlorm 3 DownM U Gmdr Dorm Gm%

Via 2l2~ll v* I Main 133 I A IWI d Main Platform 2 1 90 674 Y to R (BD-124) FC UD Goods ---+A \ GC A+&- Down Goods Shunt 305 Signal for departrogfreight train5 atte~ ' 1 1 B ] D 1Dorm~ain 1 Siding No.1

Rolle lndn Deslmatrcr~ LGLJ..... - - - -...... - -.. - - ---------- South T - Speed is 40 ht~ 101 all routes. cdntml nv Es sped Ind Oe~tinatiin llpploach lon sub WnUU Maink EPOcc tile 8 of 11 (8,1) ll\

Free Yetbw for divergence with Flashing aspects in the rear. Sleps lo Green Men DS mu@& f nex! signal showing proceed. Controlled from Red by OS occuped if flashing seplence tails. Main 124.... -- -..- -..-.- - - - - - - - - - + m e - - ~-------~--------------------'-'----"~"~'***~ South Tunnel (393m) -A,* 1 2y ' Bwifchi Dial I t 80 Approach Release fw Warner aod Catl On Aspeas -------fff------------f+--------------------***---dh-+k-***--***-m*---------- Junction F Main Running Turnouts 80 kmlh d is 40!urVh lor all routes. Appco; ch control MredIw Warning, Call On and Bjy platforms,

183 $ : Track Circuit Block G A BF *-Down South I I/-, BD Down South A I 1 1. i -* - --......---.-. DW; T DX Up Main I nonds 183 + EX I EY +-Down Main A I IA i L 183 1 n -r Up Main -* Track Circuit Block I H! I FA 4- Down Main -

V1.215100 Institution of Railway Signal Engineers BK or BL occ ry Ind 1 R Platform 1-' Aspect Sequence Chart for Layout 3.1998 Examination.,.- yy y Ind 2 Solution..---- G R C Platform 2-'.-- G YV R ~ 1 YV Y ~ rill Down Main -. G r Down Main -. '<3 YV rill 'n1 Y R '--- Y Ind 3 Down Main-' YV y R ~ 10'1 y Down Main --+ ~ BK or BLocc R y Ind4 Down Main-' 105 R ~ 103 101 '(3 Pos 1 JI E yv Pos1JI DC oce y Pos 1 JI Down Direction (Main Aspects Only)...---- G yv Y R~ ill UpMain-. m CForCGoce y ~ Ind D G Ind D y Ind U G Ind U y Pos 1 JI (3 t-- Pos 1 JI yv 1-----4 R Pos 1 JI Y 1-----4 'rr4 QlR BHoce Ind D"{f +-DownMain OL Y R r Ind D Y Ind U 112 G Pos 2 JI Ind U GI-- Y R 106 m - Gh.-- yv G t-----i yv '<3 IndD'(3.::.:;... OL Y R +-UpMain Ql Y Ind D YVR Y R Y Ind U G j Y Ind2 y Ind3 R ~ Platform 3-' STOP BLOCKS R STOP BLOCKS CF orcg oce y Ind4 R 12s Platform 4-' Up Direction (Main Aspects Only). +-Platform1 +-Platform2 152 +-UpMain Ql R Ind U Y +-Platform3 158 R Pos 1 JI G t-- 108 +-UpBranch ~ 104 IndD'G' - G yv 1 yv y OL Y OL Up Main -.1fs r--'- Down Branch-' 121 --"- Ind D y IndU G Ind U y --"- +-Platform4 R 122 ~ \ I

~~~ ~-~-------------------------. IRSE EXAM 1999 Module 5 Question 1 Examiners' Commentary for Circulation to Candidates The question requires the candidate to do a track circuit calculation. This type of question has been included in the exam for many years. Below is a statement of the question, followed by the 4 recommended stages of an answer to this type of question. The examiners' comments are given in italics. The question: Two adjacent single rail d.c. track circuits in the same running line have identical equipment, with parameters as follows Feed voltage: Feed resistance (fixed) Relay resistance: Relay pick-up current: Relay drop-away current: Ballast resistance: Length of each track circuit: 10 volt 12 ohm 15 ohm 120 milliamp 68% of pick up 2.5 ohm km 500m The two track circuits are fed with opposite polarities. The relay ends of these track circuits adjoin. A short circuit fault having resistance decreasing with time occurs at the insulated joint separating these two track circuits. Calculate the value of the fault resistance at the moment when the resulting right side failure of the track circuits occurs, that is the track relays drop away with no trains in the area. The Answer: 1. Draw a diagram The answer to this type of question should begin with a circuit diagram. The diagram should show the components which influence the behaviour of the track circuit: rails, insulated joints, ballast resistances, feed voltages, feed resistances, relays and the short circuit, which acts as a resistance. In this case the track circuits are the single rail type, which has insulated joints in one rail only, the other rail being unsectioned, for traction return reasons.

A diagram is attached -labelled "The Question" in the bottom left hand corner. I~---------------------------------------------. *** Errors by candidates: Blockjoints shown in both rails. Same polarity in both sections. 2. State any assumptions Assume that tail cable and rail resistances are small enough to be ignored. In d. c. and mains frequency a. c. track circuit calculations, it is acceptable for the candidate to make these assumptions, unless told otherwise in the question. The candidate may omit such resistances from his diagram. 3. Decide on an approach to the calculations, and explain it There are usually several approaches that can be used for track circuit calculations. Mesh current analysis is valid, but it is lengthy and complicated and therefore not recommended for use in answers that have to be completed in half an hour. For this exam, easier methods are usually appropriate, based on Ohm's law and Kirchoff's laws. The question involves two track circuits, and they are electrically identical and symmetrical, except for the polarity of the section rail. In consequence, there will be a "virtual return" at the electrical mid point of the short circuit. At this point, the potential is the same as that of the traction return rail. A real return at this point would not disturb the currents in the rest of the circuit. The calculations therefore need to be made for only one of the track circuits, and the critical resistance of the short circuit that is to be calculated is equal to twice the drop shunt of one track circuit alone. At this point, it is suggested that the candidate should make a brief note of the proposed steps in his calculation, and check that they lead to an answer to the question that is on the question paper. Steps: Relay drop-away current Rail voltage at drop-away Ballast current Feed current Short circuit current Short circuit resistance 23

4. Do the calculations The candidate should state briefly the object of each stage of his calculation, and should follow this with the arithmetic for that stage. It is suggested that candidates record the intermediate results to about 4 significant figures. Any rounding should be left until the final result. This will assist the examiners by reducing the probability that candidates get different results when using the same methods of calculation. Calculate relay drop-away current: The critical variable in this calculation, which determines the conditions in the circuit which have to be analysed, is the relay drop-away current. The relay pick-up current is given as 120 ma. The drop-away current is 68% of this: The relay current at drop-away 120 x 0.68 81.60 ma *** Errors by candidates: Not applying the 68% factor. Calculate rail voltage: The relay resistance is given as 15 ohm. Therefore, The rail voltage at drop-away 0.816 x 15 1.224 V The electrically significant components are all connected to the section rail. The rail voltage at drop-away therefore enables the currents in these components to be determined. Calculate ballast current The characteristic ballast resistance is given as 2.5 ohm km, and the track length 500 m; therefore The ballast resistance of the t.c. 2500/500

5.0 ohm The ballast current at drop-away 1224/5 244.8 ma *** Errors by candidates: Correct theory: Ballast resistance = Ohm km / length in km, not applied. Calculate feed current: The feed voltage is given as 10 volt, and the feed resistance as 12 ohm, therefore Voltage drop in the feed resistance 10-1.224 8.776 V Current in the feed resistance = 8776/12 731.3 ma * * * Errors by candidates: Assuming that the feed current is not affected by the short circuit. Calculate short circuit current: The current in the short circuit is feed current - ( ballast current + relay current) 731.3 - (244.8 + 81.6 ) 731.3-326.4 404.9mA *** Errors by candidates: Omitting the ballast current.

Calculate short circuit resistance: The resistance of half the short circuit is therefore Rail voltage / short circuit current The resistance of the short circuit 1.224/0.4049 3.023 ohm 2 x 3.023 6.046 ohm As this is the final result, it could be rounded to 2 significant figures as 6.0 ohm. *** Errors by candidates: Applying Ohm's law as R = I / V Not multiplying by 2. For the information of candidates, an additional diagram is attached, labelled "The solution" in the bottom left hand corner. It shows the currents and voltages at various points in the circuit. This diagram was not required as part of the answer. Prepared by: K.Donnelly 020 8236 9420 June 2000

IU Joint Feed Resistance 12 ohm Section Rail Virtual return connection at mid point of fault - -.-- I ~ h FAULT? ohm 1 f Joint Section Rail J '.1 omt i 10 volt supply Ballast? ohm I TR TR 15 ohm 15 ohm r Ballast? ohm 10 volt10 supply Common or traction return rail - no insulated joints I I I -----L- 1- Feed Resistance 12 ohm IRSE Exam 1999 Module 5 Question 1 The Question L ~

731.3 ma ~ +10.0 V Feed Resistance 12.0 ohm I~ Section Rail Joint t10.0 volt I supply 731.3 ma O.OV IRSE Exam 1999 Module 5 Question 1 The Solution l Ballast 5.0 ohm 244.8 ma J, J +1.224 V I Virtual return connection at mid point of fault r--1 ~ I I Fault FAULT Current. -1.224 V 6.04 ohm 404.9 ma Section Rail Lt TR 15.0 ohm I l TR 15.0 ohm I 81.6 ma 81.6 ma 404.9 ma./ '" Common or traction return rail - no insulated joints All voltages shown are relative to the traction return rail I I I ~ I Ballast 5.0 ohm 11\ 244.8 ma O.ov Feed Resistance 12 ohm +8.776 V 731.3 ma 10.0 voltl supply.---'--,...-l-...- 731.3 ma ~

Institution of Railway Signal Engineers rruxlu.tq L. <V S-, Aspect Sequence Chart for Layout 3, 1999 Examination. Model Answer. - - G G ADocc I G OL G Y y y R ~ Down Branch-' T R ~ Down Branch-' R Down Branch-' 123 111 m ill G IndD G Pos1JI,...-- G yy Ind 0 y Pos 1 JI G 1 yy y IndD R OL 'G 1 yy y BE Time y IndD R "ROL I-'-'-' Down Main Down Main-. yy Y R ~ ~ ~ Down Main-. -. R L...- ill y R R ~ Down Main-' '-- 105 'G Pos 1 JI - 103 CFCGOccl Pos 1 JI Y 101 BEOcc y IndU 1 R OL BE Time y IndU R RoL -'-'-" Up Main -. Down Direction (Main Aspects Only), BE Time y Ind L 107 Up Loop -. m R ROL 121 Up Direction (Main Aspects Only),.-UpBranch -.-UpBranch -.-UpBranch G G G OL AFOcc IG R Y y AJOcc Y Ql QL T 110 R R 118 G Pos1 JI Pos 1 JI Y 1.-Down Main Pos 1 JI Pos 1 JI QL R - G We yy 1 I.-UpMain - Ql y G 1.-UpMain R y Pos 2JI G '-- Ql R Pos 2JI 102 Y 106 114 AFOcc G Y m S' - G Y R Qh. 164.-UpLoop

Institution of Railway 1 999 Examination. Layout 31 For use with Modules 2,3 & 6. n1dllb <2- r-~~s~~!. Signal Engineers ttrrtckgrcuit Bkdr mbtions wilh Axle Counter lt Manned + I Down Main BC -r BD I I BF Tunnel Up Main 183 OL cs 3008 cc T 4F 102 Locomotive Sidings Baking cornposh cuwe for passenger trains. A1 dimensions in metres. Loco hauled train la&. 200m S' na1106 Mulliple wit train lengh. loom R#de C h Destination AWS Not Shown. Main Line Speed 100 km 1 how (Wing = 1010m at Level). Didant Siwd kanch Line Speed &I h I hour (Blng = 8Oh at Level). I-#-. Autdc Signal Station Area, All Turnouls 8 Siding Speed 40 km pn, hour (Bmkng = 400m d Level).. Scale: Central Area Only 133600. All &dents Level. *@e*m I I I I I I I I I 1 -

I ' - I=--L-I-. 1 A 1 I I 1 1 I I 1-1 1 1 Institution of R$-il~a-~-~i-~-na 2001 Examination. Module 2. Layout I. i Candidale Number s I '* Train lengths Passenger Freight I Accelerattoo Rate All trains, Braking Rate Ali trains.......... I Permitted Speed Passenger (Main I Fast / Slow lines). Passenger (Branch lines). Freight (all lines) All other running line turnouts....- _......---, Required Headway Following stopping at I00 kmlh Main lines Station dwell time Following non stopping at 100 km/h.--........ -- contracted Palhs in each direction (06050100) I Passenger C to F (non-stopping) 4 per hour. Passenger C to F (slopping) 4 per hour. Passenger A to F {stopping) I per hour. Freight C to F 2 per hour. Slopping passenger trains use Slow fines betweer E & F. 1, Contracted Paths in each direction (01 00-0600) ' I Freight 1 ' CtoF 2 per hour. Freight C to 0 (reversing at E. running round 2 per night. via the crossovers at E, then I stabling in the loop at 8). Actual 0 Icm 2cm 3crn 4cm 5cm 1 Original Scale 1 :ZOO0 Check Scale I i I Gradients level Represents O2~m8?f60rn I?!!! I i OO~I~ 1 Method of Working I. he method of block working on all running lines should be I i shown, together wilt1 any interface arrangen~ents. I I ' 2. The method of facilitating the reversal of freight trains I 1, I at Station E should be shown. I I 3. The method of working of passenger and freight trains over I the single line branch between A and E should be shown. i

- - - - OW 0020 bm0 O!W'-dlM,-0140 0169 01M 03% 0220 0240 02% 02M bxkl MM OW3 03M; 0380 bi Calculation Velocily in rids (v) = (Sped In Kdh ' mlkm)l(s~ondslminukj Bra Station A. 1 Is r 04 1 R + Up Branch Down-+ Specia! controls lo enswe IhalM3 srgn~l dws mi cber unkss 505 ob or swal(n7 wih 2PSFJ) cx (605 mlh Z06RJ of lo ensure!ha1 a tram 1s no! de!eimd on lhe viaducl 33 is ~ t m hause W mfl swat 545 has objtnrded OMW J-6,A 4; DB Down Main -+ C - 18- FA r +-,- Tradt C~tcurl Blod with Automatic Stgrlals L - --- -... 180m!normal ovew!.......,., - Up Main DC FB 1 X ux < Up Branch Down-b + BK I X Y DK Z Down Main --> i :m.\s +Y4WS ;wm l8da {narmsl map) Y w FJ 4---x Up Main + IJI4RS ELu*.\S 607 1::2000 Olmensions in Metres o ma mo ~110 XI mao Zg-

8 Ma~n Signal 403 Rwrle; Cbss Destimtm - 0 Man Do 0rarachP01 Clsped in& App Con1 - ---- Sub lkrsdebdq G - Marn Slgnal505- A f.larn Ijm Yain 507 YXtE -. - -...-,ejq-rapp3a*;ans,o(di aseertpjj...... " '.--."" f Shun! Si na1703

J Frx tlmrg~f~cy illt8ch~ig and ddarl~mng unb. no! reqvrred Iw booked movemeors 302-1 - *r*3 Depot E zl -.l 403 2010 I 4 360m (fretgh~ t Unloading Loop A8 tarn uvmng1 i i I BE <- Up Branch Down 3 2 201A... TBOm(nwmdah) '-... - c. BF ~~alcwrtrds lo ensure //mi 505 cn 604 dm6 rm! Cleat lrrlless 652 of or signal ahead of, to ensure tha! a train Is not detained M) lh6 viaduci e : g $3?A'&?. WHHS d#n (height bain Qandage) -?Down Main + f...... FE 18E5SB FG +x Up Main-, A fi'm >%.i+abis I I 409 i > e... l.w..i~~.~!.ou.er]a~l.,...,.+ BM I -r BN <- Up Branc I I 1 I t' FL 187rn-, 4- Up Main -+ T I bw m x wo 0010 cw P~SS IWO IOM 1010 1960 IMG $ 1 ~ irn 1140 1160 tiso ino 1220 1241 1x1 lm

4y< I Cripple Siding 055n 1 m + r,.l9?!-a!.?!a?!. &... L......,.... f83m (apcrcam mlrd b buept-xj -3 BHO BH r...... T :J'W; Short biakig kwn 3n8 rnfigarod bywle sfafing al40km;h.... '*fi.i?p.~[~d* R'lf~l b9rve.fnoel... I OP DP 7 I stk~s ORQ... 4- "...... s;n~rs ~m'iabbab;tnidnuo~ 'idr shti) 1P0m (nwml mierlapl M -..,..-.. r

Station E Traiu Ifam Down *: to UP Brsnch. nm rwnd w Down SlowSlow Trahs fmm Up Bmwh IP hrm Main. nm mtmd MI Up Sh, Ri~nring rmnd vda GPL 708 a d anel 4f I. I Down Siding - 4:Zm (Ire~gM train unloadmg ienglh 2 Iw kyl'

- - - Main SIP! 411 kouta cia; asanation I ~ c t A Main Dn SbW YIG b! 1 BROcc - A Call On OnSlow Occ Sub L ~ I BRQ D ~ opr 8 Main ClpSlow413 Y B C ~ O ~ U ~ S I WS& O ~ Y~US,-[ 3 it- epp CM~ -- J, A. Main S1gnal615 '~ou(e CIZ bst~nalon A Mam Up9wr113 A B kin Dom Fast 516 -. jcaii a up SWCF B Viaq Q00wnFad515 B Cali On Oow Fast OF. C Ihin UpFast617 C Call On Up Fasl Occ ;low-+ f,,... "" "'... IS lor mn rcuid! rsol?.s~werb~)...-... -------------.... I V-+ CD BET~.~ I..........* l warnnp oicnap] *-...,~iiwm.alien.ap,....." ---,,,,. f 232. FW A ~ r i FX -- 23583... 4 - :3<... Suppeasmn rot IQquKM, W n orove mxr~...... nor oomretk m n lhrs posiriorb....... ahm.ima ~,r;;;rri'iii.ml,~... i"'isid pp &,..

+- Up Branch Dm --...- Swam Sub d Y * IkD flrq Opr ' (lain Signal 51 3. Rwte A A 0 8 Class ' Desll~tlon Main DnSIw 309 Call On Dn Sh Occ Main OownFasl515 Warn Down Fag 515 '~s~ect lndic YlYYlG JI 1 Sub YPIYK; Y & h nt DR Om Mlin DS DRQ Opt DRQ Opr Main Signal 412 Main Si -. Route C ~SS I ktnralbn iasped I Mic 1 App 8 I~ain I~wn~ainsl2l~/YY!~I 4 ti AH A Down Slo...... 180n' P"*l?='?p; %... 1h3n1 ( ~~cac~cmyror lor omgencei CD M=~+-;T: CEQ CE & f- up S~OW..8G,8p-,..h.i "i,, L,-t I t 1 237 ' A ED (1 Down Fas...!s31" lagpch -'rct fore8w!sense:!.....i 23$B'g f I 8Cm ~ m mrnw n I. 11t*, G A Fl>?5l GBQ GB ; -. 618 1,... --.. 18011; (nbimal&h$""',,...... 0727 Os24 mi, + Up Fast I

!-- - ; Candidate Number 1...! rt=;yj Do~n Slow 308 Un D fl+ 4 3 Al Track Cimril Block d h Au!oma%c Signals J

2004 IRSE Membership Examination Sample Answer and Commentary: Module 1 - Question 2 (Draft April 2005) QUESTION: You are responsible for the safe operation of a railway currently operating with human drivers. An upgrade to driverless Automatic Train Operation is being considered. Outline the approach that you will take to identifying the hazards and risks associated with this proposed change and select or devise appropriate control methods. Identify what you believe to be the top 3 safety concerns for passengers and railway staff that would arise from the change, ranking them in order of significance. Briefly explain why you have included each in your list and suggest an appropriate method by which it could be mitigated. ANSWER: The following text is from a candidate's actual answer. The candidate achieved a distinction on this question: The approach taken would be to raise a risk assessment structure as outlined in the "Yellow Book". This provides best practice guidance for the safe implementation of change on the railway. The process is a seven stage process which ensures that all hazards have been identified and appropriate measures have been put in place to control the risks arising from the change. 1. Hazard identification This process involves the capture and documentation of all hazards. This may be carried out using expert domain knowledge to carry out "what if' type exercises. Two possible methods of hazard identification and brainstorming and hazard and operability study (HAZOP). These should involve people with expert domain knowledge and all sections should be involved including designers, installers, testers, operators and maintainers. All Hazard identified should be recorded in a hazard log which should be record details of the hazard identified and any assumptions associated with it. 2. Causal analysis The next stage for each hazard is to identify possible causes of the hazard. There may be a number of possible causes of a hazard. The causal analysis may be carried out either qualitatively or quantitatively. The choice being made based on the size of the risk. Qualitative assessment is based on judgment of the individuals involved. It is usually easier and quicker to carry out but may produce less accurate results. Qualitative assessment is very accurate but usually requires complex software packages and large amounts of accurate data. Techniques such as fault tree analysis may be used. 3. Consequences analysis The next stage is to identify the consequence of each hazard being realized. This again may be carried out qualitatively or quantitatively. Techniques such as an event tree analysis may be used. 4. Loss analysis The next stage is loss analysis. This is where the potential loss arising from a hazard is assessed. Loss may be classified in terms of loss of safety (i.e. incident), environmental loss and commercial loss. The above three process allows the risks presented by each hazard to be ranked. The risk presented by each hazard is a measure of its likelihood multiplied by its frequency. In order to mitigate a risk there are a number of things which may be done. 5. Option analysis This stage determines the options which may be used to mitigate a risk. Each option must be costed in terms of time and resources required. 6. Impact analysis The impact of each option on the risk must be quantified to determine if a particular option reduces or increases the risk, this assessment is carried out during this stage. 7. As Low As Reasonably Practicable (ALARP) 37