UPDATED 12.50pm: Since the start of the official holiday road toll there have been 373 crashes on New Zealand roads and three lives have been lost.

This year's toll is currently on par with last year and police say they are "cautiously optimistic" there'll be fewer deaths this festive season.

On Christmas Day, one person died in a three-car crash on State Highway 1 at Oakleigh, near Whangarei, and two died in a Boxing Day crash on State Highway 1 near Tokoroa.

National road policing manager Superintendent Steve Greally said he was pleased the toll wasn't any worse than the 2014/15 period but said: "one life was even too many".

Mr Greally said fatal crashes were particularly heartbreaking this time of year.

"They've had their loved ones on Christmas Day and then they're lost."

He told drivers to expect delays on the roads as people left the main centres for their summer holidays and urged drivers to take extra caution on the roads.

"We hate to see people make stupid decisions for being frustrated."

As people hit the roads after Christmas, traffic started to build around the country, including on State Highway 26, south of Paeroa, a common hotspot for holiday traffic.

"Today we traditionally expect a lot of people to starting leaving the main centres and making their holiday getaway," a transport agency spokeswoman said.

"People should allow plenty of time for their journey so they don't get impatient. When they get impatient, that's when they make bad decisions. Plan well and allow plenty of time for your journey."

The transport agency has advised drivers to "expect significant delays southbound on the Waikato Expressway at Pokeno for traffic turning left on to SH2" heading towards Coromandel and Bay Of Plenty.