Traffic on State Highway 1 on Kapiti is backed up for kilometres following a gas main leak.
The highway is down to one lane and is being controlled by a stop/go sign between Beach Rd, Paekakariki and Whareroa Rd, and at Mackays Crossing.
The lane is kept open for five minutes for northbound and then for southbound traffic.
Those looking to travel via Kapiti should consider using SH2 as an alternative route.
Police say they don't know when the road will fully re-open.