Somebody else can do the diagrams but here goes
First of somebody known as the PICOP, Person in Charge of Possession, takes a total block of the lines that will be affected, this done using Section T3 of the rule book, so possessions are often referred to as "T3s"
The Signalman checks that the sections of line concerned are free from traffic, and then prevents trains from entering these sections by placing the protecting signals to danger.
He Signalman tells the PICOP that his part of the job is now done. The PICOP then phones the Hand Signalmen and asks them to place detonator protection at the entrance and exit to the possession. This is 3 detonators and a flashing red stop board.
Next up depends on the area.
In DC land, the PICOP phones the Electrical Control Room Operator and requests an isolation of the traction current on all lines within the possession. There might be some jiggery pokery with hook switches but we'll leave that bit.
After confirming he has isolation, the PICOP phones the Engineering Supervisor, to ask him to test the conductor rail and apply a safety device known as Short Circuiting straps. These stop the conductor rail becoming accidently re energised
Another conversation and the PICOP gives the ES permission to start work.
The ES then phones various Controllers Of Site Safety to give them permission to start work.
Trains are booked in and out of possessions at set times, by now the first train should be approaching. It's signalled normally until it reaches the signal protecting the possession.
The Signalman phones up the PICOP and asks permission for the train to approach the possession limits. The Signalman authorises the driver to pass the signal at danger and approach the possession limit markers
The PICOP phones the Hand Signalman and asks him to lift the detonator protection, to allow the train into the possession. The Train goes into the posession and the Detonator protection is replaced behind it
Various trains are needed for a possession. One to be loaded with scrap track panel and the odd wagon for general scrap {off cuts of rail, old signalling equipment etc}.
Another train will have hoppers ready to be loaded with old ballast
Another train with have earth movers and ground rollers which are unloaded in the possession.
The old track is cut into 60ft panels and lifted onto flat wagons and taken away.
The RRV machines will dig out the old ballast and the formation below it, to a set level.
Then the ground is prepared for the new formation. It's rolled flat and a membrane put down.
New ballast is laid on top of this in several layers. The new sleepers are laid out in a set spacing and there alignment checked. The rails are then thimbled onto the sleepers using a special attachment for the RRV.
The rails are then attached to the sleepers using key. Then the ballast is laid onto the new track and abit of kit known as a regulator comes along and tidies up the ballast, ready for tamping.
The track is tamped and then regulated again. If there is time, it's the rails are then 'stressed' to create fully functioning Continuous Welded Rail {CWR}
Trains and machines exit the possession in the reverse sequence of how they came. They approach the possession limits and the PICOP asks the signaller for permission to let them out. The Signalman agrees, Detonator protection is lifted, train leaves and protection replaced.
COSS sign out and the ES removes his Short Circuiting Straps. He signs out with the PICOP. The PICOP re energises and gives up the possession to the signalman.
All between the last train Friday night and first train Monday morning
