Northfields terminators. Are there Northfields starters?

[pethadine82]

The service on the Piccadilly line has not been great post covid. It’s normal to wait 15 mins. There are times waiting at Acton Town for there to be 2 or sometimes 3 Northfields terminators. I get on one hoping there might be a service originating at Northfields going to Heathrow but this never works out. What is the reason?

 

[bcarmicle]

Piccadilly line services originating at Northfields will (generally) be travelling eastbound, not westbound. The service reason for terminating there and (then restarting services eastbound) is likely that it's considered beneficial to keep a higher intensity service in central London.

From an operational perspective, https://cartometro.com/cartes/metro-tram-london/index.php?gpslat=51.498054&gpslon=-0.314244&zoom=7 shows the track layout in the area. The only westbound platforms at Northfields are P1/P2, and the only way to put a train onto those platforms from Northfields Depot either requires a train to travel in the wrong direction onto P1/P2, or to enter eastbound via P3, travel past the points, and reverse onto P2. There's similarly no easy access to Boston Manor.

This means that by far the easiest way to start a westbound service from Northfields Depot is to start it in passenger service at Osterley, and this is in fact what is done in the early hours when the service is starting -- see for example https://content.tfl.gov.uk/wtt-60-piccadilly-18-july-2022.pdf, page 10, train 244.

 

[Mojo]

You do however get some trains on Night Tube starting at Northfields going toward Heathrow, this is to enable trains that have been out all day to be changed over.

 

[MaidaVale]

Services terminating at Northfields are usually only for specific purposes such as scheduled terminations for reasons such as staff/train changeover or if they're reformed/short-terminated to mitigate a delay (unscheduled).

The former reason (scheduled) tends to end up heading Eastbound as that's just what seems a logical choice, there are far more and far busier stations east of Northfields than there are west. There is also the reason mentioned by @bcarmicle around the points layout for Northfields depot.

The latter reason is down to the fact that a service will usually be reformed/short-terminated at Northfields due to a more significant delay, meaning that the train would end up back onto its originally booked timings by terminating at Northfields and waiting until the time it should have been following if it was heading back from Heathrow as planned before it continues back Eastbound from Northfields. The reason that trains are seldom (if ever) shorted to terminate at Northfields from Heathrow is that for it to make sense to do so, the train would most likely have to be over 1h30 mins behind schedule leaving Heathrow. This is an unlikely scenario anyway although if it did occur, a service controller would normally have tried to resolve that delay far earlier on.

 

[LU_timetabler]

There are scheduled Northfields reversals on most regular service patterns.

 

[notverydeep]

Aside from the 'high peaks', when there is a short period of time when all services at the West end of the Piccadilly line extend beyond Northfields or onto the Rayners Lane / Uxbridge branch there are three trains per hour (tph) that start / terminate at Northfields. During the Saturday afternoon period of 24 tph in Central London, the number starting / terminating at Northfields increases to 6 tph. At other times, extra trains start or terminate at Northfields as they start from the depot or stable...

 

[JonathanH]

Are district line trains still able to reach Northfield to reverse if necessary? Does it ever happen?

 

[Mojo]

Are district line trains still able to reach Northfield to reverse if necessary? Does it ever happen?

It would only usually happen for westbound trains when the wrong signal has been lowered and accepted at the junction after Acton Town.

In addition to requiring a pilot, as District line Train Operators would not be familiar with the route, S7s can theoretically operate empty Acton - Northfields, provided they are the only S-Stock in that track section on the

• Westbound local line subject to a maximum speed of 30mph (where the line speed is lower this must additionally be observed),
• Westbound fast subject to a maximum speed of 40mph
• Eastbound local subject to a maximum speed of 40mph

S7s may additionally reverse via 7 Siding at Northfields and a maximum of 3 may stable in Northfields depot, plus 1 reverser (they are limited to certain roads only within the depot).

All in all it is something best avoided. I am rather unfortunate in that the last two incidents I have been involved in of a S7 going to Northfields, both were cases of wrong signal lowered and accepted; one was where the train failed to stop with the back car on the current rails and drove it all the way in (this caused a problem because you are not allowed to plug the S-Stocks into the overhead shed leads), and the second involved something on the roof of the train snagging on some low-hanging pigeon netting under the bridge at Northfields, bringing it down and blocking the lines for anything to run west of the station!