A crash is causing delays for those travelling over the Rimutaka Hill Road.
A car rolled about one kilometre from the summit on the Upper Hutt side of the road around 12.40pm.
Police say two people are injured, one with moderate and the other minor injuries.
The NZ Transport Agency has stop/go traffic management in place and is warning motorists to expect delays.
There is a snowfall warning in place for the Rimutakas with showers set to turn to snow from 3pm.