Variable Dwell Time Indication

railtechnician I believe it is fully automatic, although the headway signal was still functioning as usual at Finsbury Park.

@dave72 Depends on who you ask. The official briefing says wait until the clock goes to zero and then carry out platform duties. In practice today the clock went down to 2 seconds and then changes back to no regulation. I gave a cab ride to a couple of the engineers involved in the project and their understanding was close doors at 5 seconds so ready to go at zero.

EDIT - Just looked again at my briefing note and it states that the system will be used by service control to smooth out the gaps in the westbound service. So maybe it's not as automatic as I thought.

Many thanks jardine01, I suppose if successful they will set it up for Eastbound workings to in time. Seems a really good way of regulating the service simply and effective as well. Wonder if they will do it on other lines that are not ATO yet.

That's why it can be turned off or modified - set up how often they want to send a train through so they don't build up a backlog of trains but don't cause queues in the central area

As is said yesterday I was held at Wood Green for 30 seconds so it must be active there as well. I've been off today so will see what happens tomorrow.

Hyde Park Corner eastbound has a balance headway signal, which can hold trains for up to 6 minutes if required.

Interesting system, and hopefully will reduce the not too uncommon Piccadilly Line bunching. If drivers don't depart promptly, I could see delays starting to develop. Maybe the "calculated" time should err on the shorter side of the average?

Paris Metro had an interesting regulation system which is now being phased out with resignaling. At the terminus the driver would be given their departure time in minutes and seconds (e.g. 34:15) by a clock. There are rarely conflicting moves out of Paris termini, so departures are usually bang on time. Then at each station, there is a delayed clock (with multiple options for times of day) which is delayed by the journey time from the terminus to that station. Thus at each station, the driver departs when the clock shows 34:15. This system however, will not solve bunching if a train is delayed, other than telling the delayed driver how much time they need to catch up.

On Vienna's Line 6 is another system which shows deviance from timetable, and counts in 5 second steps. So if a train is running on time it will show approx -0:25 secs upon arrival, and departure should be at 0:00. If a train is running 1 minute late, it will show +1:00 at departure time. I don't know if the "timetable" can be adjusted on the fly. Observations showed that drivers were unable to make up lost time anyway.

Just to confirm that it is still broken.
More money thrown at something that doesn't work!

Well I happen to think it's a great idea and money well spent.









I also think leg warmers were a much needed addition to 1980's fashion and that all motorcycles should be fitted with ashtrays.

I understand that it's been turned on again and that trains will not be held on the VDTI at each station by more than one minute.

Somebody did say some decades ago that computers without eyes could be more of a problem than a solution - - - how true!!!

Not true. The Piccadilly line's measured at four separate places chosen to give an accurate reflection of the service.

Finsbury Park westbound, Hammersmith east, Sudbury Town east and Hounslow West east.

Don’t look too closely for a scientific reason those particular sites were chosen!

Finsbury Park west is an indicator of the westbound service going into London. Incidentally, that site gives problems with the proxy score as the balance headway’s still in effect. Missed headways can be caused simply by the balanced headway holding a train for thirty seconds longer than anticipated as the threshold for a missed headway’s quite tight.

Sudbury Town eastbound gives an indicator of the service coming back from Rayners Lane and beyond. Piccadilly line trains are often held up by the Met, so the proxy score is taken at Sudbury Town to reflect those problems.

Hounslow West east gives an indicator of the service from Heathrow.

Hammersmith east is an indicator of the overall service going into London.

The average of all four sites then gives us the line proxy. As you can see, they really were chosen to give a true picture of the service provided by the Piccadilly line.