Contractors working on the Waihua Hill stretch of SH2 just south of Wairoa are advising motorists to be patient and to strictly observe a temporary traffic light system.
The lights will operate 24 hours a day for the next few weeks and there will be delays.
The area is one of four sites on SH2 between Napier and Gisborne where sections for new passing opportunities are being built to ease delays caused by the increased number of heavy trucks on the route.
The work site has been reduced to a single lane and delays of up to three minutes around the light signals are to be expected.
"Patience is required and motorists are requested to proceed through the site only on a green signal," a New Zealand Transport Agency spokesperson said.