Emergency roadworks on the A47 caused rush hour delays in both directions this morning (Wednesday).
Police are managing traffic at Little Fransham, near Dereham, while contractors repair a collapsing manhole on the west-bound carriageway.
A spokesman said the problem had been causing motorists to swerve.
It is not known whether the cold snap contributed to the damage.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here