Four people have had a lucky escape in head-on car smash in the notorious Dome Valley, north of Auckland.

An SUV and a sedan collided on State Highway 1 at the southern tip of the valley, between Kaipara Flats Rd and Christine Place, just north of Warkworth.

The vehicles and debris are blocking the southbound side of the highway, causing a build-up of traffic.

Police say luckily everyone got out of the two cars without any physical injury.