Traffic was already a circus across NSW on Thursday as holidaymakers hit the road en masse - and then three performing monkeys joined the fray.
The monkeys, which perform for Stardust Circus, were being driven along the Princes Highway south of Wollongong on Thursday afternoon when the Nissan Patrol towing their trailer crashed into a concrete barrier about 2.45pm.
A police spokesman said the monkeys escaped from their trailer and ran onto the highway at Bombo, creating confusion among holidaymakers.
The trailer was travelling in a circus convoy and handlers quickly recaptured the animals, which were not injured.
Two south-bound lanes were blocked while the crash site was cleared, and the monkeys continued on their journey south to Batemans Bay, where the circus is due to perform on Saturday.
The 21-year-old female driver suffered minor injuries and was discharged from Shellharbour Hospital on Thursday night.
The crash caused a two-kilometre traffic jam on the Princes Highway at Bombo, one of many traffic snarls experienced by frustrated motorists across the state.
Queues heading north on the Pacific Highway at Kempsey on the north coast hit 23 kilometres on Thursday and 16 kilometres at Bulahdelah, between Newcastle and Port Macquarie.
But Dave Wright, from the NSW Transport Management Centre, said traffic was expected to ease on Friday.
"We are expecting some heavy traffic again today but I doubt it will be to the extent that we saw yesterday," Mr Wright said.
He said Thursday was the second busiest day on the roads during these Christmas holidays. Queues were longer on the Saturday before Christmas.
"Usually we have two big days of holiday traffic, and we have already had them," Mr Wright said.
However he said it would only take a few crashes or break-downs for the congestion to build in some places.
At 6.30am on Friday, there were no bottlenecks reported across the state.
The cause of the recent backlogs, which have triggered widespread angst among road users, are holiday crowds combined with long-standing delays to upgrades of some of the state's major routes.
Around Kempsey, a bypass under construction will eventually resolve a lot of the congestion and allow motorists to avoid driving through the town on a road that narrows from two lanes in one direction to one.
That bypass should be finished in months, meaning this is potentially the last Christmas period in which traffic is concentrated in the area. The bypass was first proposed in 2001.
Planning started on the Bulahdelah Bypass in 2000. That road, which should also alleviate the bottleneck in the area, is due to open in March.