In a special briefing to the legislature on Wednesday, State Department of Transportation officials outlined plans for an extensive upgrade of a 3.5 mile segment of the H1- freeway between Ward Avenue and School Street.
The project is scheduled to start in early September and last a year.
Construction will involve extensive road rebuilding and repaving in at nighttime work.
The DOT has given the contractor permission to completely close the critical artery for up to 120 nights.
There will be detours, but the legislators were briefed so that they can prepare their constituents for the coming major disruptions during that time.
The federal government will pay for 80 percent of the $42 million project, and the state will allocate 20 percent or about $9 million.
This project will partially overlap with the current construction nightmare on the H-1 Freeway between Pearl City and Aiea.
DOT officials said once that portion of the freeway is redone, the road should be sustained for 20 years.