Robert Don was struck by a coach driven by Andrew Blyth at 53mph on the southbound carriageway of the A9 near Perth and suffered fatal head injuries.
Blyth was charged with causing death by careless driving. Both in his police interview and during his trial in March 2016, Blyth claimed not to have seen Don at any point; he claimed that he heard a bang and stopped the vehicle to investigate.
Reportedly, Don was visible on video footage recorded by a camera on the coach for 1.4 seconds before he passed out of its view, and 0.4 seconds later the bus’s brakes were activated. Reports do not state whether, immediately prior to becoming visible, Don was obscured by a vehicle which the bus was closely following or for any other reason or combination of potential reasons.
Jim Brunton of TRL, called by the defence, said, “From the first point of possible perception, to disappearing down the side of the bus was 1.4 seconds, which is less than the two seconds reaction time. He would have to see something first to react to it. There is no way of determining reaction time in the given period, but we allow drivers a reaction time of two seconds.”
Don was reported to have been using a single light, but it is currently unclear as to whether this was a front or rear light. He had been unable to use the cycle path alongside the A9 because it was flooded.
A jury took an hour to return a not guilty verdict.
In January 2017 Robert Don’s partner commenced civil action against Blyth.
The expert witness’s statement regarding reaction time is interesting. Assuming that the collision was not visible on the CCTV (and there is no mention of it; instead it is simply noted that Don disappeared from its view) then one, and only one, of the following must be true:
- The first event to which Blyth reacted was the bang, in which case he must have reacted by applying the brakes within at most 0.4 seconds of hearing it, or
- Blyth’s application of the brakes was in response to something before the bang.
The former would seem contrary to the expert witness’s statement, which gives a reaction time of two seconds; indeed it would make the witness’s guidance erroneous by a factor of at least five. The latter, however, would seem contrary to Blyth’s statement that he did not see Don and only braked in response to the bang.
It can be noted from the website “Human Benchmark” that the normal time to respond to an event is around 0.25 seconds—but this tests reactions to an expected event, which is known to be imminent, and to which the response is to simply flex a finger already resting on a mouse button: as test, it removes virtually all physical motion and cognitive processing from the process. It does not include mentally processing an entirely unexpected event, lifting a foot, moving it to another pedal, and pressing it down again. (Try the test here.) Note a comment on the website that a rise in average response times correlates to the rise in popularity of touch screens, suggesting that even the slight increase in motor complexity of tapping a screen has a noticeable effect in comparison to clicking a button.
It is notable that the total time from Don becoming visible to the CCTV camera to the point at which the brakes were applied would appear to be 1.8 seconds, which is close to the expert witness’s figure for an expected reaction time.