National first announced a plan for a four-lane expressway connecting Whangārei, Auckland, Hamilton and Tauranga ahead of the last election.
The cost was estimated at $15 billion for the entire project in 2020.
The maintenance of local roads was also something the party wanted to look at, Willis said.
She was asked about a range of other issues at the public meeting held at the Mangawhai Golf Club, including climate change.
Willis said she personally believed in the science behind human-led climate change, and sustainable farming was important.
Asked about the closure of the oil refinery at Marsden Point, she said she shared the views of National leader Christopher Luxon and Whangārei list MP Shane Reti.
"The reason for that is simply strategic, it seems to us that having some refining capacity here in New Zealand is a sensible step and a prudent step for the future.
"But as you know, the refinery is a private business and we respect that as a private business there is a limited role for the Government."
A person asked what National would do about over-subscribed schools in Mangawhai, and the lack of a local secondary school.
Willis said she would raise the issue with National's education spokesperson.
Willis, who is National's finance spokeswoman, said tackling the economy and the cost of living would be priorities for the party if elected.
"The number one issue we want to address is the cost-of-living crisis," she said.
She acknowledged there were global factors involved in high inflation and the rising cost of living, but said the current Government's policy also had an important role.
National wants to "put a lid on inflation" and keep interest rates stable, Willis said.
She said rents had risen under Labour due to increased taxes and costs to landlords being passed on to tenants.
When asked what National would do to improve housing affordability in Northland, she said one step they wanted to take was to remove red tape for housing developers.