Heavy vehicles will be unable to travel through a section of State Highway 7 at Lewis Pass during weekday working hours from Monday, while other motorists face delays of up to 20 minutes.

The restrictions will apply between the St James Walkway car park and Maruia Hot Springs from 12 October until Friday 11 December, as crews rebuild a 6.3km stretch of highway.

NZ Transport Agency said physical constraints at the worksite meant heavy vehicles classed as medium rigid, class 2, or above could not pass through between 7am and 6pm on weekdays.

Affected vehicles will need to use alternative routes via State Highway 1 to Nelson or State Highway 73 to the West Coast. Heavy vehicles will be able to use the Lewis Pass route overnight between 6pm and 7am, and throughout weekends.

During working hours, other traffic will be held in both directions for periods of up to 20 minutes. Motorists are being urged to plan ahead and allow extra travel time.

The rebuild will replace unstable layers of chip seal with new asphalt. The agency said the existing road surface had reached the end of its serviceable life and needed replacing to ensure safe and reliable travel.

Two full closures of the same section will also be required to resurface single lane bridges. Those dates will depend on the weather, with at least a week’s notice provided before each closure.