Engineers are working round the clock in an attempt to fully reopen the North Circular by tomorrow morning.
The road was closed in both directions as water flooded underneath the Brent Cross Flyover following a burst water main at 8am yesterday.
Thames Water has restored the pipe and is currently resurfacing one lane on the westbound carriageway which it hopes to have reopened by tomorrow morning.
The east-bound carriageway is fully open and two lanes westbound are open.
Tilling Road, which runs adjacent to the A406 and was damaged in the burst, was also reopened this morning.