State Highway 2 near Waterworks Road, Upper Hutt is now open following the two-vehicle crash this morning.
Earlier today, one person was been taken to hospital in serious condition, while another received minor injuries.
Backlogs may take some time to clear and police asked motorists to remain patient as traffic eases.
The crash was reported at about 5am.
“The Serious Crash Unit has been advised.
“The road is blocked and motorists are advised to take an alternate route.”