The round-the-clock closure is for Wessex Water is for sewer works including replacing a large manhole cover in the middle of the road.
The road is closed to through traffic from the bottom of Troopers Hill Road to the Fireclay Road/Blackswarth Rd junction. Wessex Water has apologise for any inconvenience caused, saying they are emergency works so there has been less notice than usual.
The utility company says access to properties will be maintained as there will be ways for people to divert around the works.
The road is due to be closed again later this month for planned safety improvements. The city council will be installing speed tables and speed cushions near the junction with Butlers Close, where the road passes through a double bend.