cone (something) off
Definition: to close an area like a road or part of a road using large (orange) plastic cones in order to stop people driving on or using this part.
E.g.1: There were long traffic jams on the M25 (motorway round London) because police had coned off 2 lanes after an accident.
E.g.2: There will be road works on this part of the road. The workmen will cone it off very quickly.
This phrasal verb can be separated. (E.g.2)