Motorists faced a long wait at the Rimutaka Hill yesterday morning after a diesel spill which caused at least one crash.
The hill road was closed by police for about 90 minutes until 8.30am when both lanes were reopened.
Featherston Fire Brigade chief Colin McKenna said the extensive spill covered the bottom half of the Wairarapa side of the hill.
They were called to the scene about 6am after a motorist had crashed into a barrier. The motorist had lost control because of the spill.
Mr McKenna said diesel spills can be very slippery, especially on wet roads.
"My understanding was it had been there for some time before that," he said.
New Zealand Transport Agency Wellington operations manager Mark Owen said police decided to close the road about 7.30am after the spill had caused a few crashes.
Staff patrolled gates at the bottom of each side of the hill to make sure nobody entered the road.
He said either police or contractors led motorists through the road in a "platoon" to make sure everybody was safe.
"People will probably need to take a little bit of care for the next day or so," Mr Owen said.
He said the organisation had an incident management plan in place for the hill which was followed. The cause of the spill was not known.
