(ii) when strapping was properly applied, the strapping touched all those logs resting at the top of the load across the width of the trailer.
41 The photos in evidence, particularly the photos Exhibit 1 and Exhibit 2, assist in considering the evidence which Mr Nuttall gave.
42 This brings me to the expert evidence introduced in this cause. There was no challenge to the expertise of either of the engineers.
43 Mr Colin Simpson furnished two reports. The earlier one was dated 31 July 2006 and the later one bears date 29 January 2007. Mr Simpson attended the accident site before writing the later report.
44 Mr Simpson said that the designed speed for this road was fifty kilometres per hour.
45 When he wrote his first report, Mr Simpson's conclusion was that the likely cause of the accident was
"an unusually high centre of gravity for the particular load, that unusually high centre of gravity being caused by the retention of the overall 42 tonne load but with logs of approximately 3.7 metres length as against the alternative 6 metre length for which the B-double trailers were initially (at least) configured to be loaded with."
46 Before coming to that conclusion, Mr Simpson wrote in the body of the report:
"If it is assumed that the 'average' base height of the load, i.e. the deck of the skeletal supports for the loads, is 1.4 metres in height, then the centre of gravity of the log load, i.e. half the height of the logs above ground level, is then calculated to be 2.07 metres (1.34 2 + 1.4), i.e. the centre of gravity height of the load is then at least 2.07 metres.
If the same weight of logs is placed on the trailer but the logs are 3.7 metres long instead of 6 metres, then the height of the logs above the trailer bolster or skeletal deck increases from 1.34 metres to 2.18 metres and the centre of gravity height of the load increases from 2.07 meres to 2.49 metres, i.e. an increase of 20%.
The above calculations are independent of log diameters and do not take into account the air space that must exist between the logs. Clearly, as more logs are placed on the trailer then there will be more air gaps and hence for a decrease in log length which, for a given load therefore requires an increase in the number of logs, then the air gaps must also increase in number by the same amount.
This then means that the above calculated increase in the centre of gravity height of the load of 20% is very conservative.
In summary, the effect of decreasing the log length from 6 metres to 3.7 metres, whilst retaining the same overall load, is to increase the centre of gravity height of the load through a very significant degree and, even based on a zero air gap assumption, this increase in centre of gravity height is at least 20%.
In the opinion of the writer it is this increase in the centre of gravity height of the load created by the short logs, in conjunction with the retention of the overall loaded weight, that has been of greatest significance as to the causation of the Plaintiff's accident."
47 Having attended the scene, Mr Simpson considered the significance of the S-bend configuration. With the right hand bend being followed by the left hand bend, the distance between the apex of the two bends of eighty-four metres gave rise to a pendulum effect impacting upon the load. Mr Simpson wrote, on 29 January 2007:
"With the immediate following of the right hand turn by a left hand turn, this then provides an impetus for a sharp swing of the load to the right as the left hand corner is negotiated, the swing being amplified in a pendulum motion by not only the 'g' forces applied (as per normal) in negotiating the left hand bend but also the forces in a spring like manner provided by the chassis and springs of the B-Double combination.
The lean to the right during the negotiation of the left hand bend is, therefore, amplified and with the limit being the reactive spring forces applied by the chassis and suspension system, these forces can thus be (as much as) added to those that would be applied through 'g' forces alone during the negotiation of the left hand bend.
This then makes the critical speed for the second of the bends which form the 'S' bend being as much as half that which would otherwise be the case (assuming no wheel sliding or skidding occurs, the critical factor being the roll-over only).
Therefore, with a speed of approximately 43 kilometres per hour through the (apparent) 101 metre radius of the left hand bend thus producing a single bend 'g' loading of approximately 0.144gs, the incorporation of that speed into an 'S' bend can be expected to approximately double the 'g' loading (due to the pendulum effect) to about .29'gs'. This assumes, of course, that no abnormal conditions such as an abnormally high centre of gravity for the load apply.
It would, therefore, appear probable, on this basis alone, that the additional factor involved in the Plaintiff's accident was an abnormally high centre of gravity which reduced the expected 'g' force from that reported, in the report of Mr Richardson, from about 0.35'gs' to that which probably existed at about .29'gs'.
The writer is, therefore, of the view that the 'S' bend through which the Plaintiff was driving the vehicle was a significant factor as the cause of the accident, the second significant factor being an unusually high centre of gravity for the load under the conditions described."
48 Mr Simpson considered the alternative explanation proposed by Mr Richardson that the vehicle was travelling at an excessive speed, but rejected that proposition. In doing so he had regard to the specifications of the prime mover and the gear box configuration and considered the maximum speed in fourth gear was 29.1 kilometres per hour and the maximum speed in gear five low was 36.62 kilometres per hour. He observed that the vehicle, following its rollover, came to a sliding halt over a distance measured at ten metres, and this suggested a speed at the point of impact of 36 kilometres per hour.
49 Mr Richardson reached conclusions contrary to those expressed by Mr Simpson. He furnished reports dated 9 June 2006 and 30 August 2006. He attended the scene of the accident on 26 March 2006, and he prepared a reconstruction diagram with supporting photographs (appearing on p 40 of his earlier report).
50 Mr Richardson expressed these conclusions in his first report:
"Based on the available evidence, the author's site inspection and calculations performed, it is the author's considered opinion that:
1. The laden truck critical speed for the first bend is estimated at 90km/h.
2. The laden truck critical speed for the second bend, where the rollover occurred, is estimated at 68km/h.
3. The rear trailer has slid at least 52 metres.
4. The pre-rollover speed of Mr Walker's truck and trailer combination is estimated at 73km/h to 92km/h based on a trip and roll distance of 52 metres.
5. The speed of Mr Walker's truck and trailer combination can be estimated at 60km/h to 87km/h based on a gouge distance of 38 metres (assuming that the effective friction factor for the sliding truck and trailer combination is similar to a motorcycle).
6. Based on the roadway geometry and the distance that Mr Walker's logging truck rolled, the author would estimate the speed of Mr Walker's truck and trailer combination was most likely greater than 68km/h but less than 81km/h."
51 Earlier, in the body of the report, Mr Richardson wrote (at p 34):
"Based on the rest position and orientation of Mr Walker's truck and trailer combination it is the author's opinion that the rear trailer has rolled onto its side and dragged the other trailer and truck also onto its side. The post collision scene photographs provided indicate gouge marks in the roadway in the second bend, refer to Figure 2. The rest position of the logs also indicate that the trailer has rolled when exiting the second bend. Based on Figure 2 to Figure 17 and the attached Reconstruction Diagram, the author estimates that there are gouge marks indicating the trip of the rear trailer in the roadway at least 7 metres prior to the corner fence post and the rest position of the rear trailer at least 45 metres from the corner fence post to the end of the trailer. It is the author's opinion that the rear trailer has tripped and rolled at least 52 metres. Height et al reported an empirical method to determine pre-rollover speed using the rollover distance and a rollover friction factor of 0.4 to 0.65. Based on Equation 2 the pre-rollover speed of Mr Walker's truck and trailer combination is estimated to be in the range of 73km/h to 92km/h…
The post collision scene photographs provided indicate gouge marks in the roadway in the second bend, refer to Figure 2. Based on Figure 2 to Figure 17 and the attached Reconstruction Diagram, the author estimates that the rear trailer was sliding and gouging the roadway for 38 metres. There is no test data for logging trucks gouging and sliding on dirt roadways, however given that effective friction is a dimensionless parameter the author considers that the effective friction factors for a tumbling motor cycle could be representative (Lambourn reported effective friction factors from 0.37 to 0.79). Based on Equation 2 the sliding speed of Mr Walker's truck and trailer combination is estimated to be in the range of 60km/h to 87km/h.
Based on the roadway geometry and the distance that Mr Walker's logging ruck rolled the author would estimate the speed of Mr Walker's truck and trailer combination was most likely greater than 68km/h but less than 81km/h."
52 Mr Richardson supported his conclusions by reference to two equations set out at pp 34-35 of the report.
53 Mr Richardson joined issue with Mr Simpson's conclusion that the centre of gravity height of the trailer combination was increased by twenty percent. Mr Richardson wrote as to this:
"With respect to vehicle loading, Mr Colin Simpson presents:
o That the trailers were 'modified', however, Mr Colin Simpson does not justify or prove how the trailers were modified.
o Mr Colin Simpson then presents an argument in which he claims that the centre of gravity height of the trailers involved in this collision was increased from 2.07 metres to 2.49 metres, an increase of 20% due to the modification.
s Mr Colin Simpson presents for a 6 metre length log (unmodified trailers by Mr Colin Simpson's definition) that the average based height of the load is 1.4 metres in height. Mr Colin Simpson then calculates the centre of gravity height to be 2.07 metres. However, he also presents a calculation of '1.34 + 2 + 1.4' which equates to 4.74 metres.
[The author is at a loss to understand the specific calculations presented by Mr Colin Simpson with respect to the centre of gravity height of the trailers with 6 metre logs.]
s Mr Colin Simpson presents for a 3.7 metre log length (modified trailers by Mr Colin Simpson's definition) that the height of the logs above the trailer deck would be increased to 2.18 metres, which would correspond to a centre gravity height of 2.49 metres.
[The author remains at a loss to understand how the longitudinal length of a log would affect a cross sectional area calculation. The author accepts that the length of the logs would affect the longitudinal position of the centre of gravity but finds it difficult to understand how the log length, as presented by Mr Colin Simpson, affects the centre of gravity height.
The author does not accept that the centre of gravity height of the trailer combination driven by Mr Walker was increased by 20% as identified by Mr Colin Simpson.]"
54 Mr Richardson disagreed with Mr Simpson's measurement as to the distance between the apex of the right hand bend and the apex of the left hand bend. Mr Richardson's evidence was to the effect that the distance was 150 metres.
55 The above review of their evidence makes it plain that Mr Simpson and Mr Richardson are generally at issue in this case.
56 The competing measurements as to distance indicate that the starting and finishing points over which the experts took their measurements differed. Because of the way in which the measurements were taken by Mr Richardson, I think his measurement is likely to have been the more accurate, but I am unable to resolve the distance issue precisely, because of the difficulty of determining the correct apex points. Who correctly determined point A and point B (the apex points)?
57 Ultimately I do not consider the determination of the distance to be decisive of the issue of liability even though the "S" bend was of significance in the manner perceived by Mr Simpson ([47] above). I find that the distance from one apex to the other was no less than that measured by Mr Simpson, 84 metres, and no greater than 150 metres, as stated by Mr Richardson.
58 Put shortly, Mr Simpson sees the height of the load and the configuration of the bends in the road as likely to have been causative of the accident, whilst Mr Richardson considers the likely cause to have been speed.
59 It is, of course, for the plaintiff to prove that the height to which the logs were stacked was causative of his accident. Unless the plaintiff proves this, as Mr Bartley properly acknowledged, the plaintiff must fail.
60 I propose to deal firstly with the issue of speed.
61 The plaintiff put his speed in the vicinity of 40 kilometres per hour and his evidence before me was that he was still in fourth gear when he proceeded down towards the left hand bend. In assessing the reliability of the plaintiff's evidence as to his speed, I do not overlook the fact that the plaintiff apparently told Mr Colin Simpson that he changed from fourth gear to fifth gear upon reaching the top of the incline (see [22] above). However, on this issue as to his speed, I did not conclude that the plaintiff was endeavouring to deceive the Court, and whether he was in fourth gear or fifth gear it would not have been possible for him to have approached the speed range opined by Mr Richardson. I referred earlier to the evidence of Mr Simpson about the maximum speed in fourth gear and the maximum speed in gear five low having regard to the specifications of the prime mover and the gearbox configuration (see [48] above). If the plaintiff was travelling in gear five low as he told Mr Simpson, his maximum speed would not have exceeded 36.62 kilometres per hour. If he was still in fourth gear, his maximum speed would not have exceeded 29.1 kilometres per hour.
62 Mr Richardson accepted that there were fixed gear ratios which would have governed the speed of the plaintiff's vehicle but he did not know what they were for this particular vehicle. He was prepared to accept, however, that if the vehicle was in fourth gear proceeding to fifth gear, it could not have been travelling more than forty-three kilometres per hour. He had not researched what gear the vehicle would necessarily have had to have been in in order to reach a speed of ninety kilometres per hour.
63 The photos in evidence indicate that the logs did not roll very far away from the vehicle after the vehicle overturned. The resting place of the logs that had been loaded does not impress me as being indicative of an accident occurring at high speed.
64 The investigation report prepared by Ms Quillerat was tendered as Exhibit D. Unfortunately the author of the report did not give evidence but I note that in her report, Ms Quillerat recorded that when the truck was raised to the upright position it was "found to sit within the worn driving path". Earlier, the author of the report made the like observation as to the trailers. These observations invite the inference that the vehicle was proceeding within the worn tyre tracks on the road surface when the vehicle overturned. Ms Quillerat also recorded that "tracks visible from the rear of the vehicle indicate the line and direction of the truck was within the Worn Driving Path".
65 Elsewhere in the report is a passage to which Mr Graves referred in which Ms Quillerat purported to record something of the plaintiff's account:
"Remembered descending the hill at ≈ 40-45km/hr using the jake brake and approaching from a direction slightly to the right of the worn driving path to enable him to take the corner. He looked in his left-hand mirror to be sure that the trailers had cleared the corner and began to accelerate on to the straight. He looked in his right-hand mirror and as he did so the truck went over in what he described as 'slow motion, just like being in a movie'."
66 Mr Graves invited attention to the assertion that the plaintiff was travelling "slightly to the right of the worn driving path to enable him to take the corner". I do not treat that, if accurately recording what the plaintiff said, as indicating that he was travelling outside the worn driving path at all. Certainly, the vehicle was not outside the driving path when it was returned to the upright position, if the report is accurate, and, again if the report is accurate, the tracks visible when the investigator attended the scene did not indicate that the truck had proceeded outside the worn driving path.
67 Another factor to be considered in looking at the question of speed is where the vehicle came to rest. According to the investigator, there was an indentation on the road surface where the rear bolster hit the road eight metres past the corner and there were drag marks evident for approximately ten metres to the final location. Mr Simpson regarded these marks as consistent with the plaintiff's stated speed. He considered that the distance was indicative of a speed of thirty-six kilometres per hour. Mr Richardson interpreted the marks on the roadway differently, as being consistent with the speed he opined. Mr Richardson considered that there were marks present on the road surface which indicated that the plaintiff's vehicle began to tip, and that it tipped and rolled "at least fifty-two metres" (see Mr Richardson's report dated 9 June 2006 at p 34). Those marks were influential in Mr Richardson's conclusion as to the speed at which the vehicle was travelling. The evidence as to the marks is the photograph appearing at p 18 of Mr Richardson's report, and Mr Richardson wrote that he had been provided with a number of photographs of which, presumably, that particular photograph was one. On the other hand, as earlier observed, Ms Quillerat, who had the advantage not shared by Mr Richardson of attending the scene shortly following the accident, did not detect markings on the roadway indicating that the vehicle travelled outside the "worn driving path" (see [64] above). It appears Ms Quillerat did not link the marks that Mr Richardson saw on the photograph mentioned to the plaintiff's vehicle. In the circumstances, I do not consider it would be safe to base any conclusion as to the speed of the plaintiff's vehicle in part upon the presence of those marks in the photograph referred to by Mr Richardson.
68 The marks on the road surface do indicate that the rear bolster first hit the road at a point eight metres past the corner but that that bolster did not come to rest until a point thirty-four metres from the corner, so it travelled twenty-six metres from the point where it first struck the ground. That has to be considered when looking at the question of speed.
69 Ultimately, however, I am persuaded on the balance of probabilities by the evidence given by the plaintiff and by Mr Colin Simpson that the plaintiff was travelling at approximately the speed he asserted in evidence, a speed that was consistent with what he claimed when he was interviewed by Ms Quillerat.
70 I do not find that such a speed by itself accounts for the accident or that it evidences a failure on the plaintiff's part to exercise due care for his own safety.
71 This brings me to a consideration of the significance, if any, of the height of the load.
72 What was the height of it?
73 According to the plaintiff, the crown of the load was approximately half a metre higher than the bolsters against which the outside logs would have rested. The plaintiff said he had not had a load this high before. Mr Neale Simpson, on the other hand, said that he remembered this load because it was
"not as high as the rest of them. It was below the pin height. Like the outside logs were below the pin height and it stuck in my mind how low the load was. Generally they're really high. This load wasn't." (T 213)
74 Mr Neale Simpson did attend the scene shortly after the accident but he was not asked to remember the height of the load until December 2005 (T 213).
75 Which is the more reliable account as to the height of the load, that of the plaintiff or that of Mr Neale Simpson?
76 I note that Ms Quillerat has recorded in her report dated 7 August 2002 that the driver commented that the load seemed high. That comment has the date alongside it "13.8" which indicates that Ms Quillerat spoke to the plaintiff at that time. (Mr Neale Simpson's signature appears on p 1 of Ms Quillerat's report but I do not conclude that he became aware of the plaintiff's assertion as to the load being high when he signed the report.)
77 I am satisfied that to reach the maximum permissible weight of 62.5 tonnes it was necessary to load logs 3.7 metres in length to a greater height than if one was dealing with logs 6.1 metres in length. Mr Colin Simpson reported that the increase in height meant that the centre of gravity of the load increased by twenty percent at least, and I accept this to be so comparing the maximum load of the longer logs with the shorter ones.
78 It was in the interests of the defendant and of the plaintiff's employer that the maximum permissible load be carried if this proved to be possible. Mr Nuttall gave evidence that there were frequent deliveries of less than the permissible weight in the case of 3.7 metre logs. He was asked these questions and gave these answers (at T 182-183):
"Q. …Now you frequently deliver less than 62 and a half ton?
A. And we did then.