You need a permit if you are undertaking 'street works' or 'works for road purposes', as defined in s48 of New Roads and Street Works Act.
Street works means works of the following kinds executed in a street:
- placing and inspecting apparatus
- maintaining, altering or renewing apparatus
- adjusting and repairing apparatus
- changing the position of apparatus or removing it
Works for road purposes are works of the following descriptions executed in relation to a highway:
- works for the maintenance of the highway
- any works under powers conferred by Part V of the HA1980 (Highway improvement works)
- erection, maintenance, alteration or removal of traffic signs on or near the highway
- construction of a crossing for vehicles across a footway or grass verge or the strengthening or adaption of a footway for use as a crossing for vehicles
Specifically, you will need a permit if the works involve any of the following:
- breaking up or resurfacing any street
- opening (lifting covers) in the carriageway or cycleway of traffic‐sensitive streets at traffic‐sensitive times
- any form of temporary traffic control as defined in the Code of Practice for Safety at Street Works and Road Works
- reducing the lanes available on a carriageway of 3 or more lanes
- the works require a temporary traffic regulation order or notice, or the suspension of pedestrian facilities
- a reduction in the width of the existing carriageway of a traffic‐sensitive street at a traffic‐sensitive time