M27 closure causes gridlock across Southampton
The road network in Southampton is "gridlocked" after a planned motorway closure caused severe delays.
The M27 is shut between junctions 3 and 4 for works on the 1,000-tonne Romsey Road Bridge.
Stagecoach South said one of its services had been delayed by 90 minutes.
But Southampton City Council said the motorway, which was supposed to be closed until Monday morning, could reopen on Sunday.
Five cruise ships are also due to dock in Southampton on Saturday, adding to congestion.
The closure, which leads to up to 55 miles of diversions, has been described as the "biggest traffic diversion ever in the country".
BBC Radio Solent travel journalist Joe Carden said: "There's queuing up from the southbound M3 at Eastleigh at the moment, the M271 is also looking really heavy.
"All parts of Southampton where you link up to the M27 are looking really heavy, as is the official diversion route."
Southampton City Council warned there were long delays on Basset Avenue, Winchester Road, The Avenue and Burgess Road.
Tweeting from its Southampton Travel Twitter account the city council advised residents "don't use these roads unless you have to".
Linda Holtby wrote: "Truly epic motorway closure planning on the hottest day of the year, and when there are events planned all over for Armed Forces Day."
Tim Underwood tweeted: "Please don't go anywhere near Southampton this weekend. The M27 closure has gridlocked everything!"
The motorway was not due to reopen until 05:00 BST on Monday, but the city council tweeted that work on installing the new bridge was going well, and "that will hopefully mean" it could reopen on Sunday.