A truck has rolled on the Wellington Urban Motorway, State Highway 1.
No one was injured but the southbound lanes have been blocked.
Diversions are in place via The Terrace off-ramp.
A Fire Service spokesman said a small tanker carrying bitumen rolled on a section of the motorway near Clifton Terrace.
The truck rolled onto its side but the driver was not hurt, he said.
Meanwhile, a Wellington City Council truck slipped down a bank and against a garage in Tawa this morning.
Council spokesman Clayton Anderson said the truck, which had a woodchipper on the back, was being used to prune trees away from wires on Woodstock Terrace when the accident happened sometime between 9 and 10am.
"It slid down a bank and it's come to a rest against a garage and it's damaged the garage's roof," Anderson said.
"Nobody was injured and, yeah, basically we don't quite know how it happened but we're investigating it."
A crane is expected to come in about midday to lift the truck out.
A police spokeswoman said police had been notified about the incident, as the road needed to be closed while the truck was removed.
Police say thousands of people were affected by today's convoy.