The Dartford Crossing is partially closing for seven nights.
The busy route is shut in one direction every night for the rest of the week.
It is the final round of closures on the bridge so that National Highways can conduct repairs and maintenance work.
The route is one of the busiest in Europe with up to 180,000 vehicles using it at its most hectic.
It was designed to handle 135,000 vehicles a day, but the average is now 150,000.
The work started on the west tunnel on Monday and is running until Friday night between 9pm to 6am.
The same tunnel will be closed on Saturday from 10pm to 5am.
On Sunday, the east tunnel will be worked on between 10pm to 5am.
