Evidence
11 The trailer was approximately 32 feet long, with three axles at its rear each with dual wheels. When the hoist was fully extended the front end of the trailer was approximately 28 feet off the ground, and the back end of the trailer rested on the dual wheels of the rearmost axle with the other dual wheels off the ground. It was common ground that it was important that, when tipping, the whole of the vehicle and in particular the rear dual wheels of the trailer were on level ground.
12 The trailer carried approximately 27 tonnes of BPF. BPF was powdery in form, and was apt to absorb moisture causing it to be sticky so that, when the trailer was elevated, it would not always fully discharge from the trailer. This was known up to Brambles, and to Mr Sandy and other drivers, and failure of a load of BPF fully to discharge was a regular occurrence. In Mr Sandy's experience, up to about 7 tonnes had stuck in the trailer. It stuck around the hoist well at the front end of the trailer, and particularly if (as happened) it stuck on one side or the other there was increased potential for instability when the trailer was elevated.
13 In order to counter the stickiness of the BPF, sometimes a bed of coarse coal product was placed in the trailer before loading with BPF. It was left to the operator to determine whether the BPF being loaded was unsuitable or should have a bed of coarse coal; according to Mr Michael Barclay, at the time the transport manager for the coal preparation plant -
"The process was if it was deemed that the material was somewhat sticky and the driver and the loader operator did not feel comfortable, they would then put the coarse reject material in to act as a liner, if you like, or a buffer on the bottom."
14 At the Colliery vehicles transporting BPF would reverse towards a stockpile and deposit their loads. The vehicle first reversed onto a spur of formed and kerbed roadway, and then onto natural ground closer to the stockpile. While the evidence was a little obscure, it seems that the trailer was not reversed up to the stockpile, but the load was tipped on the tipping area away from the stockpile and would then be stockpiled by a front end loader. Mr Sandy and Mr Barclay both referred to the front end loader pushing up the BPF into the stockpile, and to windrows from the front end loader pushing up BPF and from spillage from the bucket of the front end loader. The photographs to which I shortly refer showed BPF covering the end of the formed roadway and what had been natural ground from there to the stockpile, and windrows distant from the stockpile and as far out as the end of the formed roadway. For this to have come about, there must have been tipping of loads then picked up or pushed by the front end loader. The front end loader was also used to clean up fallen BPF and to keep the tipping area even.
15 The area approaching the stockpile was wide enough for two vehicles to stand side by side depositing their loads, but subject to any windrow affecting their position.
16 Mr Sandy was an experienced truck driver, and had been driving for Brambles since 1989 including transporting BPF in vehicles of the kind here involved. The load carried in Mr Sandy's truck on 18 February 2000 was his first load carried on the shift. He described it as "like damp powder with moisture in it". It was not placed on a bed of coarse coal material.
17 When he arrived at the Colliery Mr Sandy reversed the trailer towards the stockpile. He said that when he brought the prime mover and trailer to a halt he noticed that the trailer was "unlevel", and saw that its wheels had mounted a kerb and a windrow of BPF. From a photograph, he identified the kerb and the windrow, and said that tyre tracks visible on the windrow were the tracks of the prime mover. The kerb visible in the photograph, the whole area being covered in BPF from which it protruded, was at the end of the formed and kerbed road.
18 It is appropriate now to describe two photographs to which considerable attention was given in the appeal. They were taken by Mr Barclay when he attended the site after the accident.
19 Photograph Ex 1A, the photograph just mentioned, was taken looking from the prime mover end of the vehicle as it lay on its near side, towards the stockpile. It showed on its right the underside of the rear part of the prime mover, and beyond it wheels of the trailer as the vehicle lay on its side. Tyre tracks could be seen in front (as the photographer stood) of the rear tyres of the prime mover closer to the ground, but not obviously aligned with the tyres. In the centre of the photo was a windrow with tyre tracks up to a peak in the windrow, the extent of the windrow and any tracks beyond the peak not being visible because in dead ground left by the peak. These were the tyre tracks which Mr Sandy said were the tracks of the prime mover. To the left of the photo was the kerb of the roadway. The foreground showed BPF covering the end of the roadway and what had been natural ground, apparently all the way to a stockpile in the background although obscured by the windrow and the fallen vehicle. The photograph Ex 1A was marked with an arrow A pointing to the kerb, with an arrow B pointing to the windrow, and in the course of Mr Sandy's evidence with "TM" on the tyre tracks in front of the rear tyres of the prime mover.
20 Photograph Ex 1B was taken looking in the same direction as photograph Ex 1A, but with the photographer more distant from its subject so that the whole of the vehicle could be seen lying on its near side. The kerb could be seen on the left of the photograph, and more obscurely the windrow, and they were marked with arrows A and B respectively. What appeared to be a small heap of BPF could be seen on the extreme left, adjacent to the kerb but more distant from the stockpile than the end of the kerb, and a largish windrow of BPF could be seen on the right between the photographer and the front of the vehicle as it lay on its side. Mr Barclay said that this was where a load had been tipped before being pushed away and stockpiled, tending to confirm that loads were tipped on the tipping area away from the stockpile. Tyre tracks and a small depression could be seen in the BPF in the foreground.
21 Mr Sandy was not asked to describe with more precision the position of the trailer wheels in relation to the windrow when he first reversed towards the stockpile, or the extent of the windrow. In cross-examination he said as to the windrow in photograph Ex 1A that "you wouldn't even back a trailer over that", and he also said that before he repositioned the vehicle the trailer was leaning to the right but it overbalanced to the left (speaking from the point of view of the driver). He was not asked to explain further.
22 According to Mr Sandy, having seen that the trailer was unsatisfactorily positioned he -
" … drove the truck three metres forward, put it on what I designated as being the road surface, and it was level at that point, and that's where I proceeded to tip."
23 More than once in his evidence Mr Sandy referred to driving forward about three metres and then tipping, without saying that he again reversed towards the stockpile. He marked on a copy of photograph Ex 1A, which became part of Ex O, "where the prime mover wheels were, which is there, put where the steer wheels were" after he re-positioned. Two "Xs" were marked approximately on the line of the tyre tracks going up to the peak of the windrow, but some metres more distant from the stockpile. It is hard to say from the photograph how many metres but it does not appear inconsistent with about three metres. If Mr Sandy meant by the two Xs the two front (steering) wheels of the prime mover, the front of the prime mover must have been turned though ninety degrees. Probably he meant that the X closer to the stockpile was the rear wheels of the prime mover and the X further from the stockpile was where the "steer wheels" were. That is consistent with his evidence of moving forward about three metres.
24 Even allowing for difficulties of perspective in photographs, the prime mover lying on its side in photograph Ex 1A does not appear to be three metres forward of the tyre marks in the windrow, and another photograph Ex R1 appears to have the rear wheels of the prime mover as it lay on its side level, in the sense of distance from the stockpile, with the crest of the windrow. However, this was not explored with Mr Sandy; nor was he asked more precisely how driving three metres forward affected the position of the trailer in relation to the windrow.
25 Mr Sandy denied that the tyre tracks "TM" in photograph Ex 1A were tracks of his vehicle, and said that they were the tracks of another vehicle or the front end loader and were not dual wheels.
26 Mr Sandy said that he was satisfied, by looking in the vehicle's rear vision mirrors, that the surface was "flat, smooth and level". This can not be taken literally, as there was the windrow: he must have meant that the vehicle, or more particularly the rear wheels of the trailer, appeared to him to be positioned on smooth and level ground. He engaged the trailer hoist and began to tip. Tipping meant that the wheels of the trailer moved towards the prime mover. When the trailer reached almost its maximum elevation Mr Sandy took his foot off the brake, as was normal so that the vehicle could move forward as the load discharged, and the prime mover and trailer rolled forward about a metre. The trailer then "lurched to the left and fell over".
27 There was evidence from an observer, Mr Geoffrey Jolly, through the tender of documents. He was employed at the Colliery as the mechanical engineer in charge. In a memorandum dated 21 February 2000 he said that the driver started lifting the trailer "which appeared to be lifting fairly square to the ground", and described how the trailer started to "swing towards the passengers [sic] side" as it reached the point where the two front axles came off the ground and the trailer began to move towards the prime mover, and eventually tipped over. In a statement dated 15 March 2002 he said that the trailer was being "elevated in the normal way during a dump procedure when it started to tip to the passengers [sic] side, and tipped over", and -
"In my recollection the prime mover and trailer appeared to be sitting flat and even on the ground during the tipping procedure. The prime mover and trailer was close to a gutter although from my vantage point I could not see if any wheels were on the gutter."
28 Mr Jolly identified his vantage point as in the vicinity of the Final Products Bin, but there was no evidence of where that was. Mr Jolly was not called to give oral evidence.
29 Mr Barclay was told of the accident and arrived at the site about forty minutes later. He took the photographs earlier mentioned, and some other photographs. He had done some truck driving himself, and had "run a fleet of coal trucks" for a number of years, but had had limited experience of driving a vehicle of the kind here involved.
30 Mr Barclay estimated that between one-third and two-thirds of the load in the trailer had been discharged, making it plain that this was not a particularly accurate measure; between nine and eighteen tonnes of BPF, with approximation, was therefore stuck in the trailer. He said that the trailer hoist was fully extended to its fourth (final) stage. He estimated that the kerb in the photograph Ex 1A was about 15 centimetres higher than the roadway, and the windrow was about 20 centimetres above "the base level". He said that the tyre tracks beyond arrow A and at the point of arrow B were tracks of the trailer tyres, which he could identify from different tyre structures for the tyres used on the trailers and the prime movers. He was not asked about the extent of the windrow beyond the peak visible in the photograph, or about tyre tracks beyond the peak. He was asked whether he saw any other tyre tracks from the prime mover or the trailer which he could associate with the over-turned vehicle, and said that he "didn't go looking for any other tyre tracks simply because I viewed that they were the tyre tracks made by the vehicle".
31 Mr Barclay said he inspected the site generally and considered the roadway adjacent to the windrow "fine to tip that form of truck on". He said there were no big holes in it, and no particularly bad rutting and that it was a "relatively flat area suitable for tipping on". However, what he could see was impeded by the vehicle -
"REWELL: Q. The question was, was there anything about the compacted part of the roadway to the right of the windrow that you could see which could cause the trailer to be uneven if it was stopped there?
A. No, it wasn't clear because the truck was at that stage laying on it and there'd been materials spilt out the side et cetera, et cetera so but what I could see of that area, it was fine."
32 There was evidence of an expert nature from Dr Barry Hill, with engineering qualifications but no experience in the operation of vehicles such as the prime mover and trailer, and Dr Neil Adams, an ergonomist and safety consultant who likewise does not seem to have had experience in the operation of such vehicles. Dr Hill gave evidence by the tender of his report and orally; Dr Adams gave evidence only by the tender of his report.
33 The re-examination of Dr Hill brought out the obvious, that the "system" of the prime mover and trailer would overturn if its centre of gravity came to be outside its wheel base. This simple truth made no allowance for the complications of an articulated combination of prime mover and trailer and dynamic forces which might operate as the trailer moved towards the prime mover whilst elevating or as the prime mover and trailer moved forward when the brake was released. It was common ground that whether the surface on which the tipping was being conducted was level, and whether it had imperfections from holes, rutting or fallen BPF affected stability when tipping. Perhaps it would have been difficult to calculate from the configuration of the prime mover and trailer, on assumptions as to the load stuck in the trailer, the out-of-level necessary for the centre of gravity of the system to come to be outside its wheel base, and to make further allowance for dynamic forces, for example if the rear wheels on one side of the trailer went into a rut as the trailer moved towards the prime mover. Neither Dr Hill nor Dr Adams attempted such a calculation.
34 That part of Dr Hill's report admitted into evidence dealt with other matters. In his oral evidence he said that the trailer and prime mover would not be unstable if on a level surface, described at that point as "essentially horizontal" and "within a few degrees", and that any "difference in height" (meaning out-of-level of the prime mover and trailer) "increases the liability of the system to be, to reach an unstable position". Dr Hill said -
"Q. What is the degree of cross slope that is needed before in your view the vehicle would begin to overturn?
A. Based on the photographs of the truck and the relative dimensions, I would estimate between 10 and 15 degrees as being a ballpark figure."
35 Dr Adams said in his report -
"If the surface over which the wheels of the tri-axle were moving had been perfectly smooth and level and unless there was some sharp sideways movement caused by Mr Sandy turning the prime mover away from the straight line, the trailer should have remained elevated without tipping to the side as it did. I have accepted from Mr Sandy's recollection and his description, including the information in his statement, that there was no sudden sideways turning of the prime mover which would cause a counteractive swinging of the elevated trailer initiating the uncontrollable tipping movement. I must therefore conclude that there was a sufficient irregularity in the surface to cause either the offside wheels to rise suddenly (and not necessarily through a very large height difference) or the near-side wheels to dip suddenly with sufficient range of movement and speed to start the lateral movement of the elevated trailer. With the bulk of the weight being in the height range of from about 12 to 32 ft above the ground (the upper two-thirds of the trailer when fully elevated) any lateral movement in the load at that height would contribute to an increasing instability as the load moved sideways and the resulting overbalancing would be virtually inevitable."