A car towing a caravan is believed to have lost control and hit the median strip near Picton Road about 12.20pm.

The car ended up on one side of the road and the caravan on the other, straddling the concrete median strip.

A man and a woman, both aged 78, were taken to Wollongong Hospital where they were reportedly in a stable condition late yesterday.

All lanes were reopened at 2.30pm.

The accident came on the eve of the school holidays with the region bracing for heavy southbound traffic thanks to an exodus of Sydney holidaymakers.

Motorists travelling on the Princes Highway and any major roads out of Sydney have been advised to expect delays and allow extra time for travel over the weekend. Traffic at Albion Park Rail, the Kiama bends, Berry, Nowra, Milton and Ulladulla is expected to be particularly heavy.

NSW Police yesterday launched Operation Phoenix, a joint initiative with the Transport for NSW Centre for Road Safety, to target dangerous driving and address the high number of fatalities on the state's roads.

Highway patrol officers will be on the roads for extended periods.

The operation runs until the annual Christmas road safety operations.

While there have been fewer deaths and crashes on NSW roads this year, Traffic and Highway Patrol Commander, Assistant Commissioner John Hartley, said drivers still needed to be alert, especially during the school holidays.

Drivers are being reminded to stop to rest every two hours or when they are feeling tired and that the use of mobile phones not in an approved hand-held device while driving carries a $304 fine.