The lack of a serious collision or worse was a blessing.
Emergency brakes applied at about 100km/h, train then passed through tight curves (as in, high friction against the train), then ran uphill and stopped after around 800m. Given that we stop V’locity trains in service brakes from that speed in half that distance, pretty hard to blame the driver.
Driver very experienced, former instructor and had thousands of runs there on that train type. Tens of thousands of trips down that hill counting steam and diesel locos. I usually apply brakes about where he initially did; beats me why it didn’t work that time. Can only assume brake computer or wheel slide system failure.
Reported that no loud or obvious wheel flats on the train, so skidding seems unlikely, perhaps the equipment was too busy trying to protect the wheels from flats that stopping became a secondary consideration?
It is notable that in the first application of the brake on Warrenheip bank, the driver was able to reduce the speed from 160 km/h to 141 km/h in 20 seconds. About 1km/h/s on a 1 in 52 falling grade, with wheel slide activated and with sand.
On the flatter section at the foot of the grade in the second application the driver was only able to reduce speed from 160 km/h to 117 km/h in 68 seconds. About 0.63 km/h/s on a much flatter grade, again with wheel slide activated and with sand.
Of course the report doesn't give us how hard the driver was braking in these two instances.
In the next 14 seconds the speed fell further to 99 km/h - the decelaration rate increased to nearly 1.3 km/h/s. In 14 seconds at an average speed of 108 km/h the train would have travelled 420 metres. Given that this distance was measured from about Humffray St, it looks like this stretch would have included the crossover to No 1 Road, which suggests that some of this deceleration was due to the energy being absorbed in the traversal of the crossover.
It's also notable that during the second brake application the wheel slide indicator remained on for essentially the entire stop, while the sanding cut out after 71 seconds. If I've counted the time reported correctly, this would be four seconds before the driver put it into emergency, and right about the time the train was probably going through the crossover.
Twelve seconds later the speed had fallen 6 km/h - a decelaration of 0.5 km/h/s on level track with the brake in emergency, wheel slide on, but apparently no sand. At roughly the end of this period the train destroyed the gates and went through the turnout, both of which would have absorbed energy. So this decelation may have included part of this.
The train came to a stand 39 seconds later - a decelaration of 2.4 km/h/s, with the brakes in emergency, wheel slide still on, no sand, but on a gently rising grade, partially on a sharpish curve, and probably including the travesal of the turnout, and perhaps the destruction of the gates.
When looking at these deceleration rates, kinetic energy is proportional to the square of the speed while the ability of the brake to absorb energy is usually constant and independent of speed. In practice this means that the deceleration rate is slower at higher speeds and faster at lower.
Finally, around the time of the Siemens broo-ha-ha, I found an RAIB report into an incident in the UK (I can't, of course, find it now). In this report a multi-car DMU had run away for several miles on an icy track due to the wheel slip/slide system releasing the brakes. While these systems are often equated to ABS on cars, the report strongly implied that purpose of wheel slip/slide systems was not primarily to reduce the distance to stop by preventing sliding, but rather to prevent wheel flats and consequent maintenance costs. With the DMU in the RAIB report, the wheel slip/slide system had essentially disabled the brake for several miles.
I would assume the final report would look at the wheel slip/slide system, the sanding system, the interaction of both with braking system modes, and the drivers' knowledge of all of this.