The NZTA advises motorists the SH2 Rimutaka Hill Road is now open, but that delays are likely as traffic backlog clears.
NZTA Wellington Operations Manager Mark Owen says road crews have successfully opened the road after spending the morning clearing ice and applying grit. Vehicles will be escorted through in convoys at first, meaning delays are likely until traffic clears.
"We appreciate it's been a long wait, and we thank motorists for their patience and understanding while we've worked to get the road safely open."
Mr Owen said contractors deserved a big pat on the back for their hard work in such hostile conditions.
Mr Owen says the NZTA urges motorists to exercise extreme caution, watch for ice, particularly in shaded areas, and to drive to the conditions at all times.
