Rotorua's congested Te Ngae Rd will become four lanes between the city and the airport under a National-led government.
Prime Minister Bill English made the announcement at Motion Entertainment on Te Ngae Rd, following a busy morning of campaigning around Rotorua and Reporoa.
There were cheers from the crowd as he made the announcement.
In a statement, transport spokesman Simon Bridges said National would start construction on the project in the next term of Government.
"National is committed to delivering the infrastructure our regions need to support our growing country. That's why we are accelerating the delivery of this critical transport project for Rotorua," Mr Bridges said.
Te Ngae Rd (along State Highway 30) links Rotorua with the city's airport and serves both local and inter-regional traffic, connecting Rotorua to the Western Bay of Plenty, including the Port of Tauranga, and Eastern Bay of Plenty.
Rotorua had experienced strong economic growth in recent years, growing 3.9 per cent in 2016, above the national average, Mr Bridges said.
"As more people and businesses choose to be in Rotorua and its surrounding districts, National wants to ensure the city's infrastructure provides for and supports future growth," Mr Bridges said.
"Te Ngae Rd supports a growing number of tourists travelling to Rotorua and growth in the region's primary industries, making it increasingly important to connect people and products to key domestic and international markets.
"This key transport route is playing an increasingly important part in unlocking the city's future growth.
"We recognise the need to meet anticipated residential and commercial growth, as well as increased traffic freight volumes and the need to provide certainty for local government and developers.
"National wants to get ahead of forecast growth now and stop congestion becoming a handbrake on the city."
It is estimated that extending the programme of work to Rotorua Airport, including four-laning, will cost $75 to $100 million. Funding for the project will be met from the National Land Transport Fund and the budget capital allowance.
"The project will be added to National's Accelerated Regional Roading Programme, which is an important part of our plan to support our growing regions. We know that when the regions do well, New Zealand does well," Mr Bridges said.
"This regionally significant project for Rotorua will expand on the comprehensive package of projects that have been delivered across New Zealand. They all improve safety, resilience and boost economic productivity and ensure centres like Rotorua have the modern, fit-for-purpose infrastructure they need to support their strong growth.
Rotorua MP Todd McClay said the four-laneing of Te Ngae Rd between the city and airport would create jobs and keep Rotorua's economy growing.
"A re-elected National government will start four-laneing Te Ngae road in the next three years," Mr McClay said.
"This is a priority for Rotorua and a priority for me as local MP. For the first time in a decade our city is growing quickly. This road has now become urgent and today Bill English made an absolute commitment to build Te Ngae Rd."
"The $75m - $100m project will ease congestion and make Rotorua even more appealing. Our businesses will be better connected to the the Port of Tauranga and it will free up land to build more homes."
Mr McClay said the road would improve safety along State Highway 30 and also include upgraded walking and cycling facilities.
"Future-proofing our local transport network will see Rotorua become more attractive to businesses looking for a location to set up and will mean local and regional traffic can move about more easily and more safely," Mr McClay said.
"We are already the most beautiful region in the country, soon we will also be one of the best connected too."
Deputy mayor Dave Donaldson gave the closing speech following the announcement.
"This is certainly an extremely important and exciting announcement for Rotorua," he said.
"The four laning of Te Ngae Rd is, in the view of Rotorua Lakes Council and the airport, something that certainly has to happen."