8.4.2 Isolation of work area. As far as is practicable working areas should be blocked off from the active parts of the movement area by the erection of physical barriers. This is to both warn pilots and preclude work vehicles inadvertently straying onto the movement area. Any barriers must be marked for day use and adequately lit by night. The lights of taxiways leading into working areas must be permanently “off”. Guidance on the marking of unserviceable areas is contained in Annex 14, Chapter 7.