All lines that are shown in the Sectional Appendix as being in use are under the control of the Operating department (or whatever title it goes under this month).
The Engineer takes "Absolute Possession of the Line" when he wishes to undertake work, and it is this phrase from wich the word Possession is taken. It was officially known as an "Absolute Possession" to indicate that no trains could pass through.
The control of the line(s) under Possession pass to a Person In Charge of Possession (PICOP) who in effect becomes a form of signalman. He controls the movements of the engineering trains passing along the line between worksites/into/out off the Posssession, and gives authority for work sites to be set up. He will also make arrangements for the local control of level crossings where so required.
Individual "work sites" are set up, within which the actual work is carried out.
The Engineering Supervisors who manage these work sites are responsible for the safety of the line and for ensuring the work has been completed to the correct technical quality, now through a series of compliance forms that were introduced by Balfour Beatty Rail for their sites after a series of incidents by many different Contractors on other worksites.
