Signalling on Thameslink line to Bedford

[voyager1]

Can someone please explain in English how the signalling system works when a single train is delayed?

For example, when travelling on the 1800 St Pancras to Luton East Midlands service, it can get delayed because of the 1806 St Albans to Bedford Thameslink train getting delayed as that normally uses Platform 4 at St Albans (which the East Midlands train whizzes through).

When the Thameslink train gets delayed, sometimes it gets diverted to Platform 2 - to enable the East Midlands train to pass uninterrupted and other times, the signaller decides to red light the East Midlands train to allow the delayed Thameslink train to use Platform 4 at St Albans (thereby delaying the East Midlands train).

Is it a person who decides what to do or is it done automatically by a computer? Is there a particular protocol used? for example, does a delayed train always get priority even though its much slower and will cause a knock on delay to a faster train?

Sorry if this seems a stupid question but when travelling home on East Midlands, it can get frustrating when being held up at St Albans because someone or something decides its a good idea to let a slow train in front of a fast train - which then causes problems for the fast train passengers who are connecting on to other train or bus services at Luton that leave a few minutes after the scheduled arrival of the East Midlands train.

 

[Bald Rick]

It is always a person who decides, albeit a different individual depending who is on shift.

What might seem like a different decision will be made based on the overall circumstances, with the intention of minimising overall delay.

For example crossing 2W50 (the Thameslink train concerned) to the slows at Radlett might delay a southbound EMT and / or a northbound slow Thameslink, in which case it would stay on the fast line. In another scenario, there is an all stations Thameslink train due to terminate at St Albans on the down slow line at 1805, this takes a few minutes to clear and move to the turnback siding; so if that is late, then a late 2W50 would be stuck behind that for a further 5 minutes or so, potentially delaying the next train on the slow lines also.

Also, there is another fast train between 2W50 and the 1800 off St P, the 1755 Sheffield. So the slowing down of the 1800 is more likely to be being behind the 1755 which has itself caught up 2W50. Indeed both the 1755 and 1800 have 1.5 minutes pathing / performance time in their schedules approaching St Albans, and the same again in the Bedford area, which in practice means they are booked to slow down as they catch up 2W50, which crosses to the slows at Harpenden, and can make up the lost time by Bedford.

 

[AM9]

It is always a person who decides, albeit a different individual depending who is on shift.

What might seem like a different decision will be made based on the overall circumstances, with the intention of minimising overall delay.

For example crossing 2W50 (the Thameslink train concerned) to the slows at Radlett might delay a southbound EMT and / or a northbound slow Thameslink, in which case it would stay on the fast line. In another scenario, there is an all stations Thameslink train due to terminate at St Albans on the down slow line at 1805, this takes a few minutes to clear and move to the turnback siding; so if that is late, then a late 2W50 would be stuck behind that for a further 5 minutes or so, potentially delaying the next train on the slow lines also.

Also, there is another fast train between 2W50 and the 1800 off St P, the 1755 Sheffield. So the slowing down of the 1800 is more likely to be being behind the 1755 which has itself caught up 2W50. Indeed both the 1755 and 1800 have 1.5 minutes pathing / performance time in their schedules approaching St Albans, and the same again in the Bedford area, which in practice means they are booked to slow down as they catch up 2W50, which crosses to the slows at Harpenden, and can make up the lost time by Bedford.

Given that the interaction between up & down and slow & fast trains on the MML is complex in the peak (to put it mildly), do the staff at control have any tools to 'test' the tweaks that they regularly make, i.e. similar to the computer models that are used by Formula 1 teams to optimise pit stops and tyre change effects? Or are such tools as time/distance charts for the working timetable all that is availble as a visualisation aid and final decisions are based on prevailing weather/loading/gut feelings?
If they aren't available, is it likely that when the new full TL timetable is operational (including ATO), that some tools will be provided to cope with the fluctuations at the ATO/normal interface?