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11. After traversing the section from Marston to Shrivenham, 2 miles 836 yds., in six to seven minutes, viz., at an average speed of 21½ to 25 m.p.h., the leading part of the mineral train passed Shrivenham box between 5.14 a.m. and 5.15 a.m., travelling at 10 to 15 m.p.h, according to the evidence, Driver Davis having applied the brake before passing Ashbury Crossing distant signal at warning, in preparation for the diversion of the train into the goods loop. (The train was 370 yards long, and would have taken ½-minute to pass at 25 m.p.h.)
Assuming that speed was 25 m.p.h when the division took place, 1 mile, 1,650 yards before reaching Shrivenham box (where the broken piece of draw-hook was picked up), it may be estimated that, at an average of 20 m.p.h (allowing for 15 m.p.h when passing through Shrivenham), the train covered this distance in about six minutes, and that the time at which the division occurred was 5.14 a.m. to 5.15 a.m. minus six minutes, viz. 5.8 a.m. to 5.9 a.m.
In decelerating from an initial speed of 25 m.p.h, to a state of rest, under their own momentum, on the falling gradient of 1 in 834, the brake van and five wagons traversed the distance of 1 mile 1,650 yards minus 1.064 yards (the distance of the point of collision from Shrivenham box) plus the length of six vehicles, 42 yards; viz. a net distance of 2,388 yards. Assuming constant deceleration, at an average speed of 12 m.p.h., it may be estimated that this took 6½ minutes, and that the vehicles therefore came to rest at 5.8 a.m. to 5.9 a.m, plus 6½ minutes, viz. at 5.15 a.m., or nine minutes before the collision occurred.
It is clear that the assumed average speed of this train cannot be much reduced, as the period taken to cover the distance of 1 mile 1,650 yards (from the point of division to the box) could not have been much more than six minutes, because the train was recorded as having passed Marston Crossing complete at 5.8 a.m., and the failure took place 946 yards ahead of that box, to traverse which distance would have occupied about a minute.
If it be assumed, however, that the failure took place as late as 5.9 a.m., at a speed no higher than 18 m.p.h. (accepting the lowest estimate), the vehicles would have taken 9 minutes to come to rest at 5.18 a.m., again assuming constant deceleration at an average speed of 9 m.p.h.
On the other hand, calculation by a retardation formula, assuming resistance at 10 lbs. per ton, and making allowance for the falling gradient of 1 in 834, indicates that an initial speed at least as high as 25 m.p.h. was necessary for the vehicles to run as far as 2,130 yards. Indeed, the fact that they ran 2,388 yards suggests that the initial speed may have been a little higher, in which case, as in the first illustration, it would appear that the vehicles might have come to a stand rather earlier than 5.15 a.m.
These calculations do not confirm Guard H. E. Chandler's evidence; on the contrary, they indicate that he might have had as much as nine minutes for protective action. According to his own statement, he appreciated that deceleration lasted for about seven minutes, as compared with the above estimates of 6 and 9 minutes. Taking account of his suggestion that his watch may have been a minute slow, he also estimated, and indeed affirmed, that this period commenced at 5.15 a.m. "minus a couple of minutes" plus one minute (for watch inaccuracy), viz., at 5.14 a.m.; he stated that the period persisted till the vehicles had come to rest, when, at 5.20 a.m., he looked at his watch again, which time, corrected in his favour and according to his evidence, should be 5.21 a.m. Thus, he suggested that there was an interval of no more than two or three minutes between the time of the vehicles coming to rest and the time of the collision.
It is quite clear that Chandler's account breaks down in respect of the important time, between 5.8 a.m, and 5.9 a.m., when deceleration commenced, viz., when the division occurred. Had this happened at 5.14 a.m.. as he suggested, while the train was passing Shrivenham box (when Signalman Head transmitted the Entering-Section signal to Ashbury Crossing), the broken drawhook would not have been found two miles in rear of the box, but somewhere near it, and the detached vehicles would have come to a stand some distance ahead of the box instead of where they actually did. In fact, Chandler had failed to obey Rule 148 (b) and (d): he had neither kept a good look-out, nor had he applied his brake, although he thought that this heavy train was being stopped
