The New Zealand Transport Agency is warning motorists about major roadworks starting on May 21 along State Highway 2, Takitimu Drive.
The works will rebuild the northbound lane between Elizabeth Street and Chapel Street, which carries most of the heavy traffic towards the harbour bridge in Tauranga.
Bay of Plenty system manager Rob Campbell said motorists could expect significant delays for the next three weeks.
He asked them to use an alternative route if possible.
"This road is very busy with around 25,000 vehicles using it per day, and at peak hour we can see up to 2000 vehicles per hour.
"Our contractors will be working day and night six days a week to get the job done as efficiently as possible.
"The work has been programmed to minimise noise at night as much as possible, but some people may hear machinery operating overnight."
He said most of the road section was 15 years old.
Campbell thanked community members for their patience and asked drivers to take extra care through the work site.