Drivers trapped for hours on the highway between Wellington and Lower Hutt last year when the road flooded will welcome news that special gates are being installed to prevent similar incidents.

Hundreds of motorists were stuck in their cars for hours when heavy rain flooded the northbound lane of SH2 to Petone last year, the day after the Kaikoura earthquake.

Wellington and Lower Hutt were cut off from each other when the median barriers collected water coming down from the hillside, keeping it from running off the other side of the road.

The New Zealand Transport Agency announced this week it was starting work to install three median barrier gates along the stretch of highway, which would allow traffic through to the other lane in a major, traffic-blocking event.


"For anyone stuck in traffic when the floods hit last year, these gates will come as a welcome relief," Wellington Transport system manager Mark Owen said.

"Essentially traffic will be directed in through one gate and out through the other. Whether they are needed for a flood, slip or major incident like a crash, the gates will allow traffic to continue to flow, albeit at a reduced temporary speed."

The gates will be placed at strategic locations along the road, replacing three corrugated guardrails installed within the concrete median barrier.

Made of reinforced steel and weighing three tonnes each, the gates took more than six months to design and construct. They have been designed to be easily removable, yet will maintain median barrier safety requirements.

In the event of a major incident blocking lanes for several hours, the gates will allow emergency traffic controllers to open up the median and, with the help of police, move traffic through to the other side.

The gate structures contain wheels and a jack operated by a lever so they can be raised off the ground and swung open easily. The gates are pinned at each end so they can open at either end or be lifted out of the way altogether.

It will take three to four weeks of night works for the gates to be installed with crews working Sunday to Thursday nights, weather permitting, between 7pm and 5.30am.

The lane closest to the barrier in each direction will be closed to allow crews to work to remove the existing guardrail and install the new barriers.