Northern line TBTC

Neither do I, but the change in operator did coincide with the increase in delays! The change certainly wasn't just down to the swap from being a mainly class 321 operation to a mainly class 350 operation, as the class 350s were already in use and I don't recall any such delays in Silverlink days.

Under TBTC the door buttons are not activated until the 'Accurate stop' visual illuminated, which in turn will only happen once the system confirms the train is correctly berthed (or to use correct TBTC terminology, 'docked').

In reality this has added anything up to 3 seconds onto dwell times, although of course under the old way of doing things drivers are taught to stop the train and take their hand off the TBC before pressing the door open buttons, in reality seeing doors open just as the train comes to a stand is not uncommon.

The accurate stop on the Northern Line is actually more precise than the stopping marks, as it's possible to stop fully within the green section and still have to inch the train forwards.

A more annoying delay when driving in PM is that if you move the handle too quickly to the motoring position when leaving a station, the train will not take power. I've no idea why this has been designed into the system, as it's a total nuisance especially if the platform is on a gradient as the train can roll. This is not about waiting for the pilot light, it really is about moving too quickly from braking to motoring. It only happens at station stops, you have to move to off and release and wait to hear the various relays clicking, before then moving slowly to motoring.

Incidentally the next phase of TBTC on the Northern has been held back for about 3 weeks in order to allow some additional testing time. They are still 'on plan', just not quite as ahead as they would have been under the current programme.

No not Mill Hill, single track running is looking good. Just one or two things to iron out around the Highgate area.

It will be interesting to see how the next section goes. My personal view is that this next section will start to expose some of the inherent weaknesses in the system. The layout at Finchley Central is more fiddly than it looks, and the inflexibility of the system will also present challenges at East Finchley when out-of-course situations occur.

Regarding Mill Hill, there were some software issues, like the system having a capability to route multiple trains on to the single line (totally safe as each train would be fully protected by the system, but obviously inconvenient once the second train approaches Mill Hill and comes to a stand outside the occupied platform!). There were also some issues with the shuttle train entering Finchley Central Platform 1 ex Mill Hill and the effect this had on trains approaching from East Finchley. I presume there have been software upgrades in the last few weeks / months so maybe some of these issues have been worked around.

Notwithstanding the above, it is not fair to blame TBTC for some of the issues which may occur at Finchley Central, for if the site being conventionally resignalled I don't think the current setup would even come close to meeting present-day signalling standards (e.g. the double-ended trap points / sand drag off the end of Platform 2 which has no 'terminal protection' to speak of even though it is effectively a buffer stop, and the trap points for trains entering Platform 1 ex Mill Hill, to give two issues which immediately spring to mind).

Was on the northern yesterday evening and the driver came on the P.A as we approached Totteridge and whetstone. Sounding fed up of the constant power brake power brake he said: i apologise for the poor ride quality since West Finchley. This is because the computer is driving the train and it isn't as good as the driver. So we will be braking and accelerating for the remainder if the journey. Must be a tad frustrating leaving it for a computer to drive when you know you can give people a much more smooth ride.

Last time i spoke to the engineers, the system doesn't have a coasting capacity. It will always run on motors / brakes, like the DLR does. The Jubilee line also does the motors / brakes thing unless a driver is manually driving in PM. What they may be able to do however is adjust the severity of the action.

Not sure what this means but full coasting capability wasn't a part of the spec for the system in PPP days and energy efficiency wasn't something for which there was a sufficient financial incentive for the Infracos to invest in. The issue with the hunting (acceleration on/off - there shouldn't be any braking) around the target speed I think appears worse at lower speeds. Possibly for some reason the 95TS doesn't deal with it quite the same as 96TS. However, if changes are made to allow a wider margin of speed before acceleration kicks in again then it reduces the overall capability of the signalling system. This will be looked at once the second migration section goes into service.

Presumably because either the hardware interface from the ATO system to the traction equipment doesn't support intermediate settings between zero and full power or if it does they are not to the required level of granularity, or, the software doesn't support using it in the way necessary, or LU don't want to use it.

Algorithms which start to back the power off as the target speed approaches and then assesses the impact on the acceleration before making the next adjustment are not especially difficult to implement assuming the means is available to measure speed reasonably accurately.  The balancing act is between making it too reactive and thus no better than what is there now and too conservative which increases station to station running times.

My perception on the Jubilee is that the motoring/braking toggling is not as severe as it was.  I can't say if this is because the system has been tuned a little or if it's just that I've got used to it.  I've not been on a 95ts in ATO mode so don't know how it compares.

"...too conservative which increases station to station running times..."

The answer to this is obvious though: allow overspeed aswell as underspeed. Its a question of knowing how crucial it is to follow a nominal speedlimit strictly in each area. Depending on track, weather, service, and loading conditions, speeding will give risks of different size and nature ranging from nothing to catastrophy. The art of driving and the professionalism of driving anything seems very much to be in knowing what is attainable and safe rather than just rule following; indeed its probably blind rule enforcement without justification that causes so much annoyance and anger within the population and unions. There has to be legitimate acceptance of the fact that rules are for the guidance of the wise and the following of the ignorant. Perhaps that is why a TOp worth his mettle will provide a far better ride experience for a passenger than a computer.

So a well trained skilled driver can do much much better than ATO basically...

Did the introduction of ato on the Victoria and Central lines raise similar issues? Why is the smoothness of ride on those lines not available to the Jubilee and Northern?

I've always found the ride on the Central Line under ATO to be pretty smooth. The only time you get a more lively ride is when the train is running on restrictive signals. The Central Line ATO is also good at delivering fairly soft stops, something with neither the new Victoria Line or TBTC achieve. On the Victoria Line it is forgiveable because the trains really do enter the platform to an aggressive braking curve (hitting platforms at over 40 mph). TBTC on the other hand is very poor in its platform approaches, currently the Northern Line is generally achieving about 22-23 mph. As I have said before, Woodside Park northbound used to be regularly hit at 39 mph under manual driving, now we are down to just over half that speed, and still managing a nasty jolt at the point the train comes to a stand.

Part of the problem with TBTC is the system doesn't seem to have any recognition of features such as gradient. When driving in Protected Manual mode, sometimes you can get the speedo turn from yellow to orange (indicating over target speed) without getting an 'Overspeed imminent' warning, whilst with seemingly no logic to it, other times you do. This is most annoying when running slightly early departing Totteridge, as if early the VCC will issue a lower target speed, so you're stuck to maybe 30 mph, and the only way to drive is motoring up to target speed, letting the train coast for a few seconds, then motoring for a few seconds. Every single time you reach the target speed the 'Overspeed imminent' alarm will sound, even if you've already gone to coasting at that point and on a quite steep uphill gradient there's no chance the train will actually overspeed when coasting!

My own personal opinion is Seltrac is a rubbish system, and the Victoria Line system should have been used throughout LUL as it is superior in just about every way!

The ride is smooth because the DC motors don't provide as much of a kick at higher speeds unlike the AC motors on 95/96ts, but you can tell the train is doing exactly what happens on the TBTC system especially if on a long stretch for example Theydon Bois - Debden where you can see the brake cylinder gauge needle shoot up as the brakes are applied on a very regular interval as it keeps to target speed.

You would have thought gradient is one of the first things they would take into account considering they are one of the main things to affect train speeds and so on!

Thanks for the update. Knew from London Reconnections that NMA2 was supposed to be completed this month but wasn't sure exactly when.

Let's hope tomorrow all goes well or passengers, engineers and managers alike!