In the last days before the first Covid lockdown, I was on a Mk4 set heading North that was consistently showing on my GPS&GLONASS device as 131mph. Back in BR days we used to time trains between the mileposts, calculated an HST at 135mph once and a 91&Mk4 set at 140mph down Stoke Bank. I guess the signalling system wasn't capable of catching out speeding drivers back then. The fastest a class 91 has gone in testing with a shortened 5+DVT is 162mph.
Class 91 could run at up to 140mph for short time. There are flashing green aspects on sections where they could do that speed. The track staff were not allowed on track at the times they ran due to insufficient warning time to stand clear. When new HST's often got well over 125mph but damage was being caused to the drive train and they fitted a speed limiter. I got a 91 from Kings Cross a few years ago. We departed 20 late and had almost made up time by Doncaster then they let a slow service in front of us. That day I had a GPS and we ran at 132mph for some distance. These days it is hard to recover lost time with the over speed systems. The Lumo at Peterborough managed to avoid being tripped by accelerating after passing the over speed system, the driver convinced he was running through on the fast when in fact he had been slowed to turn onto the slow accelerated to 75mph before realising he was turning off. A close shave that day.
The train can technically operate above the limit. It’s the TPWS (train protection warning system) grid overspeed sensor that will activate an emergency brake demand on the train if operating above a limit. For example. My train has a maximum of 75mph. If im going 85mph on a 90mph section, i will be able to continue. But the OTMR (on train monitoring recorder) will send a warning to the train maintenance that it has been operating 10mph above the maximum speed, and the driver will be in a deep world of trouble. If i was going 60mph in a 50mph zone, the TPWS overspeed sensor times when a train passes 2 sensors on the track. If its at a certain speed above it, the train will activate a TPWS brake demand, and again, driver will be in a whole world of trouble.
