Motorists may be forced to drive to get to the other end of the M27 from later in the month.
The motorway will be closed in both directions between Junction 3 and Junction 5 for bridge replacement repair work.
The roadworks are set to take place between Friday, September 28 and Monday, October 1.
And the main diversion route will take drivers up to Salisbury and onto the A34 before coming back round to the M27.
The M27 is being closed in both directions between Junction 3 and Junction 5 while Highways England replace two bridges over the motorway.
The current bridges are said to be ‘unable to move as originally designed’ and are nearing the end of their lives – with cracks appearing in the concrete beams.
The £19m scheme is set to be completed by January 2020, with further motorway closures next year from April 26-29 and October 18-21.
There will be another local diversion, as well as contingency plans for emergency services.