The New Zealand Transport Agency (NZTA) removed barriers just after midnight clearing the way for motorists to use the 7.5km section of highway between Orewa and Puhoi, just north of Auckland.
The Government has waived the $2 toll for cars and the $4 toll for trucks until midnight tomorrow, the end of Auckland Anniversary weekend.
NZTA's regional director for Auckland and Northland, Wayne McDonald said heavy traffic along the Northern Gateway motorway was expected today and tomorrow.
"We will be using radio as well as roadside electronic message signs to help make sure people keep moving," he said.
The new highway provided motorists with a safer and more direct route between Auckland and Northland, he said.
It featured reduced gradients, smoother curves and clear sight lines.
"The benefit of the electronic toll road is that you do not have to interrupt your journey to use it," Mr McDonald said.
There were no toll booths on the road and people could pre-pay before they travelled, or up to three days after they used the road, he said.
If people did not want to use the toll highway there were free alternatives routes on the Hibiscus Coast Highway and SH16 from Wellsford in Northland and Auckland.
By Friday NZTA, had collected more than $300,000 from nearly 7000 motorists who had opened pre-pay accounts to use the road.
The money was held in a non-interest bearing trust account.
The cost to every motorist who opened an account was $40, with an additional $4 for every nominated light vehicle using the same account.
As they used the road the toll was automatically deducted and when the account dropped to $28, another $28 was automatically put into the motorists' accounts from their own bank or credit card.
For account holders the toll was automatically deducted from their account after they passed under gantries at the southern end of the road.
On the gantries a bank of cameras read front and rear number plates, measured the vehicle and decided to deduct either a car or truck toll from the accounts.
If no account was set up motorists had three days to pay before they got a reminder in the mail.
They could also pay in advance by telephone.
The toll deduction was fully automatic and motorists did not have to stop or slow down for the toll to be paid.
The only motorists who had to stop were those who elected to pay by cash at one of two cash machines at the northern and southern ends of the motorway.
Motorists would pay no extra for towing trailers, caravans or boats and motorcyclists would not pay any toll.
