REPORT ON THE DERAILMENT

Transcription

1 MINISTRY OF TRANSPORT RAILWAY ACCIDENTS % I/ REPORT ON THE DERAILMENT which occurred on 20th November 1959 near BALNAGUARD HALT in the SCOTTISH REGION BRITISH RAILWAYS LONDON: HER MAJESTY'S STATIONERY OFFICE 1960 ONE SHILLING NET

2 DERAILMENT NEAR B ALNAGUARD HALT - 20th. NOVEMBER, 1959 R I V E R T A Y Bogias from leading coach h Trailing wheals from engine I FIG. 1 GENERAL SITE PLAN SCALE: 6 INCHES TO l MILE DETA AND ILED SITE PLAN SHOWING WASHOUT POSITION OF TRAIN AFTER DERAILMENT SCALE : 40 FEET TO l INCH 'IG. 3 CROSS SECTIONS SCALE HORIZONTAL AND VERTICAL : 40 FEET TO l INCH

3 MINISTRY OF TRANSPORT, BERKELEY SQUARE HOUSE. LONDON, W.1. 5th February 1960 SIR, I have the honour to report for the information of the Minister of Transport, in accordance with the Order dated 26th November 1959, the result of my Inquiry into the derailment of a passenger train at about 6.55 am. on Friday, 20th November 1959, near Balnaguard Halt on the single tracked Aberfeldy Branch line in the Scottish Region, British Railways. The 6.41 am. Up passenger train from Aberfeldy to Ballinluig, when travelling at a speed of m.p.h. and in almost complete darkness, was derailed at a point some three-quarters of a mile short of Balnaguard Halt where the formation had been washed away leaving a steepsided cavity some 25 feet wide and 16 feet deep under the track. The latter was still intact and spanning the gap, and the whole train, comprising a tank engine and two coaches, crossed the gap on it, beating down the far side lip as it did so and thus widening the gap to some 45 feet, and became derailed on the far side. The train was the first over the line that morning. The train came to rest with the engine, which had been travelling bunker first, lying across the track, having been lifted off its bogie, swung round through 125" and turned over on to its right side by the weight of the coaches behind it. The leading coach was derailed to the right, lifted off its front bogie and pushed up the bank, but remained upright and came to rest with its front end distorted and resting on the chimney end of the engine. The second coach was derailed but remained upright and in lime close to the track, with its rear end projecting some 9 feet over the edge of the widened gap. The front of this coach, where the guard was travelling, was torn off and the guard was thrown forward through the hole and then fell into the gap behind the train. The driver and fireman were badly shaken ; in addition the driver's back was injured and the fireman's hands and face were burnt. The sole passenger, who had been riding in the second coach, was only slightly injured and, after attention at a nearby farm, proceeded on his journey. In spite of their injuries the train crew sought aid with commendable promptness, the driver going at once to one farm and the guard to another and then on to Ballinluig on foot with the train staff. As a result a doctor and an ambulance were quickly on the scene. The single line track over the gap and for some 45 yards beyond it was completely destroyed. After repairs had been carried out the Branch was re-opened to traffic on the morning of Monday, 30th November ten days after the accident. The weather at the time of the accident was fine, after an evening of heavy rain. The railway DESCRIPTION 1. The Branch line from Aberfeldy to its junction with the main Inverness-Perth line at Balliuig is 82 miles long and was opened in It is single line throughout, with intermediate halts at Grandtully and Balnaguard, and carries five passenger or mixed trains per day in each direction. It is normally worked by the "One Engine in Steam" method using a train staff, but facilities are provided for the introduction of electric token block working when the running of additional trains makes this necessary about twice. a month. 2. Details of the area are shown on the sketch opposite. Approachig the site of the washout from Aberfeldy, the single line runs roughly from West to East on a falling gradient of 1 in 1,000 and a left hand curve of 68 chains radius ; it straightens out just beyond the site and continues straight for three-quarters of a mile to Balnaguard Halt. A few yards short of the site the line runs out of a cutting on to a sidelong cut-and-fill formation, with a slope down 35 feet to the River Tay on the left and a slope up feet to the top of the cut on the right. Side slopes are at between 1 in if and 1 in 2 and on the cut side are coarsely grassed. Deciduous trees grow thickly on both sides of the railway. The soil is hard sand and gravel, with boulders up to 2 feet diameter, and with a fair admixture of loam ; this general type of soil extends to a considerable depth below rail level. 3. From the top of the cut the natural slope of the hillside rises fairly steeply to over 1,000 feet some four miles to the South. Near the site the Aberfeldy-Dunkeld road runs on a low bank roughly parallel to the railway and some 35 yards up the hillside from it. Between the railway and the road, and beyond the road, is coarse pasture sloping towards the railway at about 1 in Some 50 yards on the Aberfeldy side of the point of washout, drainage from the road above has been led under the pasture towards the railway in a stone pipe. The upper end of this pipe is at ground level and water from a culvert under the road flows down the bank into it ; up 3

4 to the time of the washout the lower end discharged, at X on Fig. 2> into the ditch XY along the top of the cutting towards Balnaguard. In addition to taking the outflow from the pipe the ditch acts as an ordinaly catchwater drain about 40 yards long and it empties straight into the River Tay through a 3' by 2' 3" masonry culvert under the railway at Y. From X to about A the ditch is in the open and the fall is slight, but behind the length from A to beyond Y a small dell runs out of the hillside towards the river, and the cutting face is lower, so that the fall becomes steep enough for the ditch to be normally self-cleansing though the ditch runs under trees. It was the blocking of this ditch at B, and the consequent overflow of water down the face of the cutting, that was the immediate cause of the washout. 5. The track up to and over the washout was laid to Class C standard with 95 ibs. B.H. rail, with SIA chairs and steel keys, on timber sleepers on clean ash ballast. The train 6. The engine was a tank engine, 34 feet long over buffers ; it weighed 54 tons loaded and its braking power was 37% of this weight. It was hauling two similar brake corridor coaches, each with its brake compartment at the leading end. They had been built in and had wood framed bodies with steel panels and roofs on steel underframes, and each weighed 35 tons. They were screw-coupled and connected by a vestibule gangway. All glass in the coaches was 2 inch plate. The damage 7. The length and depth of the cavity under the track after the derailment is shown in Fig. 3, Cross Section 3 ; the dotted line shows the profile of the formation before the washout and the unbroken line shows the profile after it. The cavity was some 45 feet wide where the rails still spanned it, its near face on the Aberfeldy side being much steeper than its far face on the Ballinluig side. An interesting feature was the irregularity of its shape in plan (see Fig. 2); its sudden widening towards Ballinluig started at the foot of the cutting face. Some 1,000 cubic yards of formation bad been washed away. Fourteen sleepers had become detached from the rails spanning the cavity and were lying in it haphazardly and at all angles but not buried. Very little ballast was visible in the cavity, and what little was on the surface was all towards the far side. The track approaching the near side had been slewed very little, if at all, towards the river, but the rails for about six lengths had been pulled out to the limit of their fishplate holes. There was no joint in the rails spanning the cavity. The track beyond the cavity and within the area of the derailment was destroyed. The three wires of the block and telephone communications, which are carried alongside the track on wooden posts, were unaffected by the washout and subsequent derailment and communications remained intact. 8. Damage to the engine was considerable below the main frame but above it was largely superficial. Major structural damage to the two coaches was confined to the steel underframe of the leading coach, the front end of which was badly distorted, probably when it overturned the engine. The coach bodies suffered little damage, except that the front end of the leading coach was buckled by the distortion of the frame and the front end of the second coach was pulled off by the connecting vestibule as the leading coach veered to the right and mounted the cutting side. Damage to passenger accommodation was very small ; two of the plate glass windows in each coach were broken and one seat was displaced. The weather REPORT 9. During the seven days preceding 20th November 1959 the rainfall at Aberfeldy was 3.02 inches ; this is about threequarters of the average rainfall there for November (3.90 inches). During the 24 hours ending 9.0 am. on 20th November 1959, the rainfall at Aberfeldy was 1.01 inches. Evidence at the Inquiry 10. Mr. W. Milne, Permanent Way Inspector, Perth, said that the policy was for all drains and ditches to be cleaned out once in early summer, when growth was heavy, and again about December, when the leaves had fallen and there was a touch of frost in the ground. He had inspected the drains in the Grandtully length, in which this washout occurred, after the summer cleaning and had been satisfied with their condition. He had accompanied the District Engineer on the latter's annual detailed examination of the length on 21st October 1959, and it had then been awarded very high marks for a length of its class (86% including 85% for drainage). Mr. Milne's practice was to visit this length about once a fortnight and his last routine visit to it had been on Tuesday, 17th November, three days before the washout. His reason for visiting the length on that particular day was that the ganger had been repairing a curve. He had checked the radius of the curve and the cross levels and, as usual on these visits, had made a general examination of the fences, bridges, culverts and drains, though he had not paid any particular attention to the ditch XY. In spite of recent fairly heavy rainfall the flow through the culvert at Y had been no more than usual and the drains were clean and doing their job. He had also accompanied the District Engineer on a routine tour of the branch line on the day before the washout ; everything had then been in good order and well maintained. 4

5 11. A. Morton, now the ganger of the Aberfeldy length, had previously been a lengthman on the Grandtully length for 2t years. During his time there the ditch XY had never been regarded as in any way a possible source of danger ; it had done its job well and, though cleaned out twice a year as a matter of routine, had heen virtually self-cleansing. He could not recollect any previous occasion on which water had flooded down the hillside towards the road or across the road. 12. K. Rohertson, Acting Ganger of the Grandtully length, had been a platelayer for two years and had acted as ganger for one year. His length was about 4 miles and he had one lengthman to assist him. He had cleaned out the ditch XY, as part of his maintenance programme, during the summer and had cleaned it out again specially in October, after a spell of very heavy rain. By the date of the washout he had not yet done his winter cleaning because the leaves had not yet all fallen. He had examined the ditch frequently ; the last time he had done so specially was ahout three weeks before the washout and it had then heen clean and in good repair. 13. Some witnesses referred to previous earthwork trouble at or near the site, but on examination all the incidents mentioned proved to be just the kind of minor mishap, such as a fallen tree stuck in a culvert or a small slip in a cutting face, that is to he expected on this kid of line in winter. None of them had endangered the line and none of them were connected in any way with the washout or could have raised a suspicion that it might happen. There had heen no previous washout on the branch. 14. All witnesses were agreed that Thursday, 19th November, had been a clear though dnll day and that little if any rain had fallen before 6.0 pm. From then until about 10.0 p.m., however, rain had fallen very heavily indeed and had been accompanied by an easterly gale. The rain had stopped ahout 10.0 pm., and the weather had been fine but still very windy for the rest of the night. 15. The departure of the 6.41 am. train from Aberfeldy on 20th November was quite normal. No messages passed between the signal boxes at Aberfeldy and Ballinluig hut under " One Engine in Steam " working this was quite in order and, since the telephone and hlock wires had not heen affected by the washout, the signalmen could have communicated without getting a hint of anything amiss. The train left on time with Driver D. Battison and Fireman M. McGroarty shaply on the alert for trees across th5line ; previous experience had taught them that trees were a likely hazard after a gale. They saw much water standing beside the line in the early stages, but the journey to the site of the washout was generally uneventful. The left hand drive engine was travelling bunker first and, on the left hand curve approaching the site, the fireman had the better view, but in the darkness the first he saw of the washout was " something black " apparently across the line about 20 yards ahead. The train was travelling at its normal speed of m.p.h. and before he could make out what the black thing was the train was on to it. Driver Battison had just seen the lights of Balnaguard Halt and had shut the regulator, when the train began to lurch and rock as it crossed the washout. Neither of the men remember much of what followed and Driver Battison did not realise that his engine had turned on to its side until some minutes after it had done so. He was convinced, till lie had seen the gap the train had crossed, that he had hit a tree. 16. Mr. Milne reached the scene ahout 9.30 am. He found a lot of mud on the road ahove the site, evidence that water had flooded over it during the night, but the flow in the ditch XY was slight. He examined the ditch and found it to be in good order and clean throughout its length, except at B where it was clogged with short branches, leaves and silt and had become blocked. Just behind the hlock was the upper end of the washout. Ganger Morton, who had reached the site at 8 a.m., also saw much evidence of water having flooded across the road during the night. Evidence at the site 17. Fairly heavy rain had fallen shortly before I visited the site, and the conditions I saw were probably similar to, though much less extreme than those that must have obtained during the early hours of 20th November. A lot of water was flooding down the hillside ahove the road in two very wide but shallow streams. One stream was being shepherded by the folds of the hill face into a small burn which discharges into the River Tay through a 2 ft. X l ft. 6 inch dry stone culvert under the railway. The other was flooding into a long shallow pool along the upper side of the road, whence it was discharging through the culvert under the road mentioned in paragraph 4. The stream was not carrying enough water to flood over the road, as it must have done during the night 19th/20th November, hut the culvert was full ; the flow through it was such that the water was not mnning down the face of the hank into the mouth of the stone pipe, but was jetting over it. The flow through the pipe was thus quite light, and the hulk of the water was flooding down the face of the slope to enter the catchwater drain over a length of about 5 yards below X. 18. I traced the two flood streams to their source in the woods about 350 yards up the hill from the road. Here a large open ditch, which appears to form the main catchwater drain for some 170 acres of hillside, had become blocked at ahout the point Z on Fig. 1 by small branches, leaves and silt, and the water was ovelflowing it and spilhg down the hillside. The block was cleaned by two men in ahout five minutes ; it may well have formed, when the stream 5

6 was high and the wind strong, in quite a short time. The ditch was fairly fuu when I saw it; evidence along its banks showed that recently it had heen much fdler. The lie of the hillside above the road is such that if the block had formed even a short way up or down the ditch from where it did the flood would have run differently. CONCLUSION AND REMARKS 19. I have no doubt that some time during the night 19th/20th November, when more than a quarter of a normal November's rainfall fell in four hours, the ditch across the hillside became blocked at Z and a fair proportion of its water-and it must have been very full-began to flood down to and over the road and so into the ditch XY. This ditch did its job as a catchwater drain and carried the water down to the Tay through the culvert at Y, but by an unfortunate coincidence a similar block formed in it at B, and the water built up behind this block, where the bank is low, and flooded down the face of the cutting, eroding the formation and cutting a deepening " Vee " across it. 20. I think that, until the train began to cross, the cavity formed by the washout was cigar-shaped in plan, about 25 feet wide where it passed under the track and with steep sides. The train was travelling fast enough to "jump " the gap on the unsupported rails, which were held to gauge for just long enough by the sleepers, till these were shaken off : the rails sagged and each bogie in turn hit the far lip of the cavity a heavy blow, and this succession of blows beat the lip down into collapse, widening the gap to 45 feet. It is remarkable and fortunate that the complete train crossed the gap before derailment. r 21. I am satisfied that this length of lime was properly inspected and well maintained, and that the arrangements for cleaning out the ditches were sensible and conscientiously carried out. I am also satisfied that the drainage system was properly planned. It might have been better to have had the outflow from the stone pipe at X down the face of the cutting, as has now heen done in the course of repairing the washout, but it is easy to be wise after the event and the original arrangement had stood the test of time and it was not at this point that the drain failed. At no other place on this branch is there a similar ditch along the top of a cutting slope. I do not think that what happened during the night 19th/20th November could reasonably have heen foreseen or better guarded against. In my view the washout was pure mischance. 22. The train crew were properly alert and could not have prevented the accident or lessened the damage. They behaved commendably after it. 23. No one was in any way to blame for this derailment. I have the honour to be, Sir, Your obedient Servant, J. R. H. ROBERTSON, Colonel The Secretary, Ministry of Transport. (0899) Wt K A.O.St.