Repairs to the Gade Valley Viaduct and large-scale street lighting works are set to lead to overnight closures on sections of the M25 and M1 near Watford from later this month.

A notice from Highways England in this week’s edition of the Watford Observer outlines plans, in alternate phases, to close both carriageways of the M25 between Junction 19 (A41) and Junction 21A (A405) and all slip reads leading to and from the length of carriageway for repairs and maintenance to the viaduct.

The order is due to come into force on February 15 until the works are completed and during this time reduced speed limits will be in place for those parts of the carriageway that remain open.

Starting at 9pm every night, the closures are due to last until 5.30am from Monday to Thursdays, 6am on Fridays, 9am on Saturdays and 5.30am on Sundays.

Traffic affected by the closures will be diverted using the M1, A41, A405 and A414. The route will vary depending on the closure in place.

A second notice from Highways England outlines the temporary closures that will be required while work to replace the lighting, cables and cabinets takes place from a date on or after Monday, February 22.

The effect of the order will be the phased overnight closure of:

Both carriageways of the M25 between Junction 20 (A41) and Junction 21A (A405)

The northbound carriageway of the A405 from its divergence from the road leading to the northbound carriageway of the M1 at M1 Junction 6 to Chequers Lane.

The southbound carriageway of the A405 from Mount Pleasant Lane to the road leading to the recycling centre,

All the slips and links to and from the lengths of carriageway described above, including the links connecting the M25 to the M1 at Junction 21 (M1 Junction 6a)

The roads leading to and from the southbound carriageway of the M1 at Junction 6 (A405).

The road leading from the northbound carriageway of the M1 at Junction 6 (A405)

All of the side roads at junction with either carriageway of the A405 between M1 Junction 6 and M25 Junction 21A (A405).

The overnight closures will take place from 10pm to 5.30am on Monday to Thursday, 11pm to 6am on Friday, 10pm to 6am on Saturday and 10.30pm to 5.30pm on Sunday.

The work is expected to take eight weeks but the closure of the A405 main carriageway is anticipated to be for only one night, to be confirmed in advance by signage and the Highways England website.

Traffic affected by the closures will be diverted using other junctions on the M25 and M1, and by using the A41, A405, A414, Mount Pleasant Road, Station Road, Park Street Lane, Tippendell Lane, Old Watford Road, Chequers Lane, High Road, Horseshoe Lane and Woodside Road.

For full details of these works and other notices this week, go to the Public Notices section of our website via this link.