If you're travelling on the Pacific Highway next week, you'll see changed traffic conditions at the St Helena Tunnel on Monday night.

Essential maintenance work will close the tunnel overnight on Monday, February 24, between 7pm and 5am.

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

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.

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

For the latest traffic updates download the Live Traffic NSW App, visit http://livetraffic.com or call 132 701.