Those that will need to travel the M1 to the Gold Coast or Brisbane tonight and the next two nights will have changed traffic conditions at the St Helena Tunnel to carry out essential maintenance work.

Routine maintenance of the St Helena Tunnel is carried out every three months and involves a range of measures such as inspecting the various operating and safety systems.

To reduce impacts on motorists this work will be carried out at night.

The north and southbound lanes of the tunnel will be closed from 7pm to 5am tonight, tomorrow and Wednesday night, reopening at 5am Thursday 9 June, weather permitting.

North and southbound traffic will be diverted onto the Hinterland Way between the Byron Road interchange at Bangalow and the Ewingsdale Road interchange at Ewingsdale.

Motorists are advised to allow up to 10 minutes additional travel time for the diversions, drive to the conditions and follow the direction of signs and traffic control.

Transport for NSW thanks motorists for their patience during this time.

For the latest traffic updates download the Live Traffic NSW app, visit livetraffic.com or call 132 701.