Three people have been arrested following a protest on State Highway 1 in Wellington's Kilbirnie this morning, police say.
The protesters, from the Restore Passenger Rail group, had adhered themselves to the road.
One of the protesters was receiving medical attention due to the substance used.
"Police appreciate that the situation may have caused frustration for commuters and would like to thank the public for complying with diversions," police said in a statement.
Waka Kotahi said the incident was reported shortly before 8am and the route was closed to city-bound traffic until just before 9am.
Delays should be expected, it said.