Motorists encountered delays of more than 60 minutes at Kiama, where a notorious bottleneck left the highway looking like a car park more than eight kilometres long.

Heavy delays were also experienced at Albion Park Rail, where traffic began building as early as 10.45am.

Lake Illawarra Traffic and Highway Patrol police supervisor Sergeant Kevin Hood said despite the delays, motorists were behaving well.

"People have been doing the right thing for the majority of the morning," he said.

"It was really good until 10am then once the rain stopped everyone decided they would go today."

Traffic was expected to remain heavy on the roads until at least 6pm yesterday, and motorists heading south are again warned to expect delays today.

Sgt Hood said there were a few simple tips motorists could take to avoid becoming stressed behind the wheel.

"Just be patient, people who have travelled this road for the last X amount of years would be well aware of the delays," he said.

"We encourage you to plan your trip, and leave earlier or later to avoid those congested times."

"If [motorists] ... are agitated or frustrated, see if they can get out where it's safe to do so and stretch their legs.

"It might be a slow trip but you'll get to where you're going."

Yesterday marked day seven of Operation Safe Arrival, the state-wide holiday police campaign targeting a range of offences, including drink and drug driving, speeding, fatigue, seatbelt use, mobile phone use and other forms of dangerous driving.

Up until day six, police had issued 4757 speeding infringements, conducted 213,002 breath tests and laid 241 drink-driving charges across the state.

Yesterday morning, the NSW Christmas holiday road toll climbed to six after two men died on the M1 near Mooney Mooney.

NSW Police Traffic and Highway Patrol commander Assistant Commissioner John Hartley said that with a total of 241 drink-driving charges so far, motorists need to organise travel arrangements prior to going out and celebrating to get home safely.

"It is disappointing that people continue to drink and drive, with a 48-year-old man allegedly caught driving on the Central Coast nearly five times over the legal limit," he said. "With 213,002 breath tests being conducted throughout NSW in the past six days, if you are going to drink and drive you will be caught."

Double demerits will remain in place until January 1 for speeding, seatbelt and helmet offences.