Network Rail - T3 Possessions

Our ref: HSR/2/29

Head Office Circular: NP/66/23

31st March 2023

To: The Secretary




Dear Colleague,




Further to Head Office Circular, NP/50/23, dated 17th March 2023, I write to explain that I 

have received correspondence from Network Rail (NR) with an update on the trial of alternative possession limits and the current phase of the Possession Limits Control Project which is focused on T3D – signalling disconnection protection. 


In connection with this trial, I have also received a report from the Lead Officer, with an update as regards Phase 1 of the trial and intentions for Phase 2 and 3.


In connection with the above, at its meeting on 30th March 2023, your National Executive Committee (NEC) resolved as follows:


We note the correspondence from Network Rail.


We instruct the General Secretary to write to NR and RSSB (for the attention of their TOM SC [Traffic Operation and Management Standards Committee) to explain that at Phase 2 & 3 of the T3D project the use of detonators placed at the Engineering Supervisor Marker Board must be explored - to determine whether these detonators bring an additional layer of protection to track workers and trains.


Branches and Regional Councils to be informed. 


Please bring the contents of this circular to the attention of relevant members. 


Yours sincerely




Michael Lynch

General Secretary