Motorists are being warned the Dartford Tunnel will face partial closures for up to a month whilst essential maintenance work is carried out.
Highways England has confirmed the main thoroughfare between Kent and Essex will shut for evening and night time works from later this month onwards.
It is being carried out by Connect Plus Services which operate and maintain the M25 motorway network and its linking roads on behalf of the highways agency, as well as the Dartford Crossing.
They will be carrying out maintenance and repair works to a section of the Essex Viaduct, just beyond the exit of both tunnels.
It means the Dartford Tunnel will be closed during two phases in order to complete the work safely.
These closures will be in place between 8pm and 6am, Monday to Friday, starting first from Monday, August 16 to Friday, September 3, excluding the summer bank holiday on Monday, August 30.
During this time the East Tunnel will be closed and a clearly signed diversion will be put in place via the West Tunnel.
Height restrictions will also be in place for vehicles greater than 4.8m in height.
Then from Monday, September 6 to Friday, September 10, the West Tunnel, including the A282 Junction 1a northbound entry slip road will close.
A clearly signed diversion will be in place via the East Tunnel.
Road markings will be dotted along the entry slip road via the A282 southbound to junction 1b and return.
Motorists will then be able to access lanes three and four on the A282 northbound for the East Tunnel.
Highways England says works are subject to change and are conditional on weather and other factors.
For further information, or if you have any questions about this work, the agency is encouraging road users and residents to contact its customer contact centre on 0300 1235000, available 24-hours a day.
The Dartford Crossing connects the A282 road between Kent and Thurrock in Essex and is made up of two bored tunnels and the cable-stayed Queen Elizabeth II bridge.
It's the only fixed crossing of the Thames to the east of Greater London and is one of the busiest in the UK with up to 160,000 vehicles using it daily.