Northbound from East Finchley

Under the original signalling, it was rare to get an unimpeded run along this section because of the signalling design approaching Finchley Central. The home signal for Finchley Central (NQ28) was linked to the two preceding signals. NQ280A was an intermediate running signal, but also became speed-controlled if NQ28 was at danger. There was also a second signal NQ280B between the two, which used to clear at 20 mph. This design arose because of the long downhill gradient on this section. Because of the very long distance from NQ280A to the platform, it was very common for trains to reach NQ280A before the preceding train had cleared Finchley Central.

With TBTC, it's a simpler issue. I believe there are a number of speed restrictions leaving East Finchley which accounts for the first part of the slow running. However uder the current timetable, it is common for trains to arrive early at Finchley Central. If the Seltrac system calculates the train will arrive early, it imposes a maximum speed to prevent the train running too early.

My personal view is this is (another) negative feature of the Seltrac system, as it is far better for early trains to be held in platforms where the time can be more usefully used. Enforcing a slow speed delays people travelling to the next station, and combined with the poor quality of the Seltrac ATO driving also contributes to an all-round poor ride quality. Also, if you then get a delay at the next station, early running can very quickly turn in to late running, which defeats the purpose of the system. It also has a very annoying quirk that once the train has received its limit of movement authority, it seems to stick to the calculated maximum speed even if there is than a delay in departing. So for example you could arrive at East Finchley on time, the system calculate the train is running early and apply a 30 mph limit to the next station, then get a passenger alarm operation which takes 3 minutes to resolve, now depart late but still get the 30 mph to Finchley Central and arrive even later, after which the train will go at maximum speed to make up. The Victoria Line system offers a much better solution in that if running early the train will calculate a coasting point, which is a better solution all round.