Why cant TBTC stay at a constant speed??

You really should reference and credit the originator of your first paragraph here. YouTube 3 months ago.

In a platform, the target speed is about 3mph. When it departs, it gradually raises. It goes down when approaching a platform. This is really the only cruise control its got. personally, I think they should take down the system and let us drive again like in the good old days.

probably a driver fed up of ATO haha! Maybe driver training? Trainees drive in PM mode i think.

canary warf to Westminster is quite fast which means its smoother. It wasnt manually driven - the train will only do 7mph. as for underrunning the platform, well thats just the bad system.

Tbtc, why do you say the train wasn't being manually driven? Numerous JL trains every day are driven manually at full line speed, and there are many new drivers undergoing driver training in driven line speed mode - Protected Manual - the TBTC system has full in cab signalling so you can drive more smoothly than the ATO can, and you can stop short of platforms in error (and overshoot) which has also happened on and off recently. I think you need to go away and learn what the tbtc system is and what you can do with it before posting incorrect information on here again !

jardine01, yes back then not all trains were ATO 'ready' (or commissioned to be precise) and had to be driven in PM. Pretty much all trains were ATO ready after a few weeks and have been 'normally' placed in ATO mode since early 2011. However, there are still many reasons on a daily basis why you will find trains being driven at line speed in PM mode (driving to the in cab signalling display known as a TOD - train operator display). Some reasons are:- driver training, train out-of-service, trackside worker 'protection' and also on the very odd occasion, poor rail adhesion conditions. If a train is creeping along as per tbtc's description, it is in Restricted Manual and means something significant has failed on either the train or the trackside systems.
With the latest timetable in place, PM operated trains that are not 'out of service' will cause significant hold ups through the pipe, less so at the north end of the line. An out of service PM driven train doesn't have such a big impact as it has no dwell requirements in stations, so lost time between stations is made up by non-stopping.

This post is simply another tautologous one; perhaps you chose not to see or didn't understand what sw206 has now said twice in the posts above yours: there are many reasons why some trains run faster than others, the most plausible of which he's mentioned above. You have no way of knowing whether this train was running in TBTC mode or not and, frankly, does it make one iota of difference? Please take the advice and knowledge of people who might understand more about the subject than you rather than being like someone playing snakes and ladders who always has to start at '0' again; it really is getting dull.

Can someone lock this thread now, please?

I wonder if its train driving algorithm would do better with an old-style train with an electromechanical camshaft controller. If it's alternating between full power and coasting, then when it coasts, the controller would go back to its initial position, and then have to go back up through the notches, which takes some time to do. This means that it doesn't go to full power instantly, which reduces the instantaneous change in acceleration, also known as jerk. With new trains, they can presumably go from coasting to full power nearly instantly, which makes for a bigger jerk, which is what passengers are finding so uncomfortable.