Penrose bridge over SH1 is strengthened against vehicle strikes


The NZ Transport Agency is strengthening a bridge against vehicle strikes on the Southern Motorway.

It’s installing collision protection beams to protect the Penrose bridge over SH1 from further damage. The bridge has been hit 41 times since 2008, with 32 hits on the southbound side.

The 4 span bridge is made of reinforced concrete, but vehicle strikes damage the concrete beams and risk undermining the structural capacity of the bridge outer beams. Repairs are costly and disruptive to motorway users.

The bridge at its lowest point over the southbound lanes has 4.52m clearance. NZ Transport Agency rules stipulate that the maximum height for a load is 4.25m. 

The Transport Agency has an over-height detection system on the motorway, but the driver of a detected vehicle still has to pull over and stop. The collision protection beams are a last resort measure to protect the bridge.

In May 2016, a 15 tonne digger on the back of a truck set off the detection system before it hit the Penrose bridge. The crash blocked two lanes for about three and a half hours, causing significant disruption to Auckland traffic.

Installation of the protection beam on the northbound lane will be completed tonight. The beam on the southbound side will be installed in April.

The first collision protection beam is installed over northbound lanes of the bridge at Penrose on State Highway 1.