A Lineside Study of a Decade of Traction Performance Change on the Crewe – Manchester Line 1998‐2008

A LINESIDE STUDY OF A DECADE OF TRACTION PERFORMANCE CHANGE ON THE CREWE – MANCHESTER LINE 1998‐2008 David Stannard RPS railway performance society www.railperf.org.uk A LINESIDE STUDY OF A DECADE OF TRACTION PERFORMANCE CHANGE ON THE CREWE – MANCHESTER LINE 1998‐2008 David Stannard 1. Introduction 9. Diesel multiple unit workings 2. Lineside speed determination Heritage units 3. Virgin Euston‐Manchester services Sprinter and Sprinter Express units Legacy traction New generation units Pendolinos 10. Intermodal container traffic 4. Diverted West Coast mainline services Freightliner and EWS electric‐hauled Dragged VWC loco‐hauled services Freightliner and EWS diesel‐hauled Dragged VWC Pendolino services Fastline Class 56 workings Dragged Scotrail Caledonian sleepers 11. Heavy haul and other freight workings 5. Virgin Cross‐Country services China clay slurry Legacy traction Aggregate traffic VXC Voyagers and Super Voyagers Enterprise trip workings Voyager substitutes Other freight movements 6. Arriva Cross‐Country high‐speed services 12. Network infrastructure workings 7. Other loco‐hauled passenger workings Infrastructure renewal Strengthened Alphaline Cardiff services Track recording and monitoring Charter excursions Rail‐head treatment trains 8. Electric multiple unit workings 13. Light engine movements Heritage units 14. Concluding remarks Manchester Airport‐Euston services Class 323 units on local services 1. INTRODUCTION The years following the turn of the Millennium were an interesting time of transition on the Crewe‐ Manchester line, with Virgin’s wholesale replacement of Inter‐City and Cross‐Country stock with modern Pendolino and Voyager units, the introduction of new generation diesel multiple units and freight locomotives, privatisation initiatives by North Western and Central Trains extending services from Crewe through to Manchester Airport using the new southbound link, and also the frequent diversion of workings from the Macclesfield route and the Anglo‐Scottish mainline north of Crewe due to engineering work associated with the West Coast Route Modernisation (WCRM) programme all bringing an almost unprecedented richness and variety of traffic to the line. To record the performance of the different types of traction working over the route over 5,000 train speeds have been measured in the vicinity of Chelford, which is roughly mid‐distance along the line around 5 miles south of Wilmslow on a broad plateau of gently undulating grades which follows a modest but generally sustained climb from the salt ‘flashes’ south of Sandbach. The maximum permitted line speed was 100 mph up until May 2008, when after final commissioning of a new computer‐based signalling system the line limit was raised to 110 mph in readiness for the intensive West Coast high speed timetable. An initial survey was carried out between late 1998 and 2000. Subsequently there was more casual observation and monitoring through to the end of 2008, with targeted measurements made of A Lineside Study 146 July 2009 specific workings whenever new traction was introduced, following infrastructure improvements or when there appeared to have been significant changes in performance. 2. LINESIDE SPEED DETERMINATION The methodology is based on stopwatch timings of the progression of workings through the track circuit blocks of the automated multiple aspect signalling system of the line. When the front of a train passes the signal being used for measurement and enters the following block section, this will trigger the track circuit of the new section and the signal will turn from green to red. Thereafter as the train progresses down the line and the rear of the train clears successive signalling track circuit blocks, the signal will progressively change to yellow, double yellow and green. Hence the time intervals between changes of clearing aspects at a signal are a measure of the speed at which trains are travelling down the line. A complication is that timing delays associated with the detection of track circuit occupancy and with the signal switching process itself need to be taken into account. The net effect of these on timings of the clearing sequences at an individual signal is likely to be complex (effectively being the sum of differentials between all of the various signals involved). However simultaneous observations of the clearing of sequential signals (generally possible at night, albeit on curved track sometimes requiring accessing difficult to reach locations like the middle of farm fields) reveals that the time for an individual signal to change after the next signal down the line clears is to a good approximation independent of the aspect changing, of train length and of train speed. Hence in principle it should be possible to calibrate these effects and remove them from the timing data. For much of the survey period timings were made using Wilmslow powerbox‐controlled signals WW7, visible approximately 0.5 miles south of Chelford station and protecting the exit of the Up (southbound) loop, and WW12, located just to the north of the Down station platform. In each case the red/yellow ‐ yellow/double yellow time interval was used for speed determination, with the following yellow/double yellow ‐ double yellow/green time used as a check and to identify workings still markedly accelerating or braking. Daytime northbound workings in particular could sometimes be severely checked approaching Alderley Edge by signals protecting recessing and re‐starting local services or by knock‐back delays from traffic at the junction with the Styal line at Wilmslow. Wherever significant easing or braking effects were identified in the multiple block timings, these measurements were excluded from the survey so as to provide statistics on as far as possible ‘free‐ running’ traction speeds. Calibration was by direct comparison between lineside measurements of signal clearing times and simultaneous interpolated conventional ¼ milepost speed determinations made by a second person on‐board trains travelling at around 75, 90 and 100 mph. Simple mathematical algorithms involving a time offset and a speed‐time product which fitted the data over this speed range were then developed to convert signal clearing times to train speeds. Timings of Class 6 freight workings at around 60 mph and of Railhead Treatment Trains spraying at 40 mph suggested that the calibration was valid at lower speeds, and this was confirmed in the summer of 2003 when Pendolinos were timed running under cruise control at the restricted speed of 60 mph because of high track temperatures. Accuracy is difficult to quantify, but for individual speed determinations is believed to be better than 1% from the sharp cut‐offs in the speed distributions of modern traction with speed limiters such as Coradias and Pendolinos. With the timing blocks used, the effective locations for most speed measurements were approximately 1.7 and 1.1 miles to the south and north of Chelford respectively, although other signals to the south were also calibrated to provide information about northbound speeds through Chelford station itself. A Lineside Study 147 July 2009 The line was re‐signalled using new Ansaldo computer‐based interlocking technology in 2006, with signals re‐positioned at increased spacing in preparation for higher speed running. Southbound timings were made at signal MS4092, situated on the south end of the Up station platform and now controlling the entrance to the loop, with the yellow/double yellow ‐ double yellow/green time interval being used for speed determination in order to provide closer compatibility with earlier measurements made with the original signalling. Northbound timings were made using MS4085, now the first signal north of Chelford and located 0.2 miles closer towards Alderley Edge. As before, the red/yellow ‐ yellow/double yellow time interval continued to be used for northbound speed determinations, but with the increased distance to the northbound measurement signal a direct ‘station’ speed determination also became practicable from the station area by timing the interval between the front wheels of the train passing over the tie bar of the crossover pointwork immediately before the platform and MS4085 turning red. A method of ‘self‐calibration’ was adopted to deduce the parameters of again simple algorithms for the conversion of timing measurements to speeds by iteratively fitting the spread of measured signal timings to the profiles and cut‐offs of the previously determined speed distributions of individual traction types. The accuracy of speed determinations made using the main signalling blocks is again believed to be better than 1%, but stopwatch timing limitations may realistically limit the accuracy of high speed measurements made using the shorter northbound station timing block to more like 1.5%. Results for the different types of traction were plotted as speed histograms of the number of timings in integer speed bins, with southbound and northbound measurements normally combined unless there was evidence of a significant difference. Two parameters were then extracted from these distributions for summary purposes: the mean, and the 80 percentile speed range i.e. the speed band which excludes the top and bottom 10% of measurements and in which there is an 80% probability that a speed measurement will lie. To illustrate this an example is given in Figure 1 of the measured speed distribution of Class 66 locomotives on Freightliner intermodal container workings (with an advantage

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