Drivers will need to allow extra time to travel over the Rimutaka Hill Rd on Sunday.
Delays are expected between 3am and noon on Sunday as about 250 marchers re-enact the journey of World War I soldiers from Featherston to Trentham.
Traffic will only be able to pass the marchers at certain points on the route, with police escorting traffic past marchers. A pilot vehicle will also be used.
The marchers will be walking from Featherston to Kaitoke, with a memorial unveiling at the summit about 7am.
From noon, both lanes will be reopened, but the Summit and Trig Track carparks will remain closed until 5pm.
