info at met stations

what i see but on other lines the outer parts all have DMIs that tell you about the next 3 trains

There are none on Dagenham East.

Well the online data streams that TfL provide include the details. So the signalling is able to provide the information to TfL computers.

Chalfont & Latimer as an example www.tfl.gov.uk/tfl/livetravelnews/departureboards/tube/default.asp?LineCode=metropolitan&StationCode=CLF&GoMetropolitan=Go&switchMetropolitan=off

Having been playing with the data available, it appears to update based on train position and therefore this is not likely to be a signalling related issue, more an installation issue!

The DMIs on stations are (currently) fed using equipment fed from Signal Cabins and Control Rooms. Control rooms are normally equipped to supply such information, however older signal cabins may not always have such equipment.

The majority of tubelines are controlled (either entirely or almost entirely) from control rooms with such equipment. The sub-surface lines are controlled from a mixture of signal cabins (with or without such equipment) and control rooms.

The feeds you see online are taken from an entirely different area - that being an internal program called "Trackernet." This is a combine-wide program which maps train running information and on the whole does a good job. However, for areas that don't currently display train descriptions (what is shown on the DMI) or track circuit information, it attempts to make a "best guess" as to the arrival of a train based on what it has seen previously enter the "black holes" we have on our signalling system.

Yes, Trackernet could (and has been) linked to the DMIs, but you first of all need the DMIs themselves (expensive if not already installed) and you need Trackernet to be much more reliable if you're not going to incur complaints the first time it predicts something wrongly. You'll have to wait for the new signalling for everything to be updated, installed and modernised ;D

MetControl has already explained the reliability issues with Trackernet, sachil. It's more likely that TfL will get complaints about incorrect information than no information at all. Since I got a smartphone, it's been less of an issue for me, but I do note that Trackernet isn't quite as accurate on the Met as on other lines, for the reasons MetControl outlines. In any case, timetable frequencies are displayed at stations, so you should have a reasonable idea when a train is turning up, provided that a good service is running (information when delays are occurring are another topic!).

do the dmis on the east end of the district show any info? like from barking onwards?

That's because the track fuses for the bay are out meaning it thinks there's a train there.