Extreme care must be taken to avoid stationary traffic tailing back through a signal controlled junction or pedestrian crossing. When you are carrying out any works in a location where this may be the case, the highway authority must be consulted.
In these circumstances it might be necessary for the traffic signal at the junction or crossing to be turned off, in which case alternative means of controlling traffic and pedestrians, as appropriate, must be agreed with the highway authority and put in place.
Caution: To proceed with this option, at the earliest opportunity your supervisor, manager, or other competent person must consult the highway authority.