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Source: New Zealand Transport Agency

A motorway overbridge has been struck by over height vehicles twice in the same weekend, prompting urgent maintenance works, just a year after major repairs following similar incidents.

“On both occasions warning signs were illuminated, but the vehicles didn’t reduce their speed, striking the bridge at speeds up to 100km an hour. It’s fortunate that nobody was hurt,” says Waka Kotahi Auckland Systems Manager Andrea Williamson.

Visible damage was immediately identified by responding crews, with a structural inspection and emergency works carried out to remove concrete debris from roadway. Maintenance to the collision protection beam was also needed to ensure full capacity of protection was restored.

“There’s been a marked increase in the number and severity of incidents in the last two years, and that’s why we will be working more closely with police to ensure the drivers are adhering to height restrictions,” says Andrea Williamson.

Current guidelines stipulate the maximum height for a load is 4.3 metres, with over-dimension permits required when a load exceeds five metres. However, all loads over 4.3m height require written approval from Waka Kotahi for all bridges spanning over motorways.

The Penrose Road overbridge, which is 4.57m above the road, has been struck 43 times over the last decade, severely damaging the main deck beams.

Waka Kotahi is calling on heavy haulage operators and independent excavator companies to make sure drivers are aware of their surroundings or warn they risk being ticketed.

“We know the Penrose overbridge is one of region’s most restrictive, which is why we have installed additional safety features including electronic signs to warn drivers who risk hitting the bridge. It’s disappointing when those alerts are ignored as it puts the road user at significant risk of serious injury and death,” says Andrea Williams.

“Repairing bridges from this type of event is costly and often requires motorway closures disrupting travel for other road users.”

In 2018 a protective steel beam was installed in front of the bridge above both the northbound and southbound lanes. The beams are to work in conjunction with the over height detection system and signage. Following yet more strikes, the bridge plate was last year removed in sections for repairs to be undertaken. That revealed more damage than expected, with the overbridge needing to be partially closed until the bridge capacity was restored.

“Now further repair works will again be required in the weeks ahead, to restore damaged concrete as well as testing to identify any cracking or fatigue. We will advise road users of any closures ahead of time,” says Andrea Williamson.

Waka Kotahi will also be sending out measuring tools and guidelines to operators to ensure drivers know the rules before setting out.

Height (m) Operating conditions
Greater than 4.3 – up to and including 5
  1. Written permission from the owner of an overhead obstruction that the vehicle travelling underneath cannot clear.
  2. Written approval from the relevant access provide, if the vehicle travels over a level crossing that does not cross a state highway, and the vehicle exceeds the height shown on an electrified railway safe height sign.
  3. For loads exceeding 4.8m, a vehicle with a deck height less than 1.3m above the road must be used.
Greater than 5 – up to and including 6.5
  1. Need to meet all of the above operating conditions.
  2. Need a permit from OPIA.
  3. A vehicle with a deck height less than 1.3 metres above the road must be used.
  4. Need written permission from the owner of overhead wires or cables that the vehicle travels under.
Greater than 6.5
  1. Need to meet all of the above operating conditions.
  2. Need written approval from the Transport Agency: Apply to OPIA.

MIL OSI