Major gas starting in the New Year weeks will mean delays for motorists around Queens Road and Beechen Grove in the central Watford.
Engineers will start work on Monday 6 January to upgrade gas mains in Queens Road. The 15-week project will see the existing iron mains replaced with new hardwearing plastic pipes designed to last for at least 80 years.
National Grid Authorising Engineer Dilbir Chana said: "While we’re carrying out this important and essential project, we’ll make every effort to minimise the inconvenience that our work causes.
"We are sorry for any disruption caused to local people and motorists but this project is essential to ensure that we can deliver dependable gas supplies to gas users in Watford for many years to come."
Phase one will begin on January 6 between 172 and 126 Queens Road and is scheduled to be completed by February 14.
Phase two, between 172 Queens Road and the junction of Queens Road and St Johns Road will then commence and is scheduled to last 10 days. During this phase, four-way traffic lights will be in operation.
Phase three, between 126 and 96 Queens Road is due to start on February 24 with an estimated end date of March 17. Two- and three-way traffic lights will be in operation for this period.
Phase four, between 96 Queens Road and the junction with Beechen Grove is due to start on March 17 with an estimated end date of April 14.
All start and end dates are estimates only, and may need to change as the work progresses.
The work is being carried out on behalf of National Grid by a partnership between Morrison Utility Services and Skanska.