Four years and 21 bridge crashes
The bridge hit by a truck-born digger has an over-sensitive warning system that is causing false alarms, experienced truckies claim.
Truckies say certain conditions can set off Penrose overbridge’s sensors on slightly under-height loads, frustrating drivers and leading some to possibly ignoring the warning system.
Despite the warning system on Penrose overbridge, since 2012, the bridge has been hit 21 times by over height loads.
A truck driver is facing dangerous driving charges after his truck hauling a digger smashed into the Penrose bridge on May 9. The digger and truck blocked three southbound lanes for several hours causing afternoon misery for tens of thousands of Auckland motorists and an estimated $9 million in lost productivity.
New Zealand Transport Agency ( NZTA) figures show Penrose’s bridge takes the lion’s share of Auckland motorway network bridge strikes at 39 per cent.
Overall, the agency’s 254 Auckland motorway overbridges have been struck 53 times over the four years.
Auckland truck company owners Todd McGlade and Ian Spedding, who have 75 years truck driving experience between them, said the overbridge’s approach warning system placed several hundred metres before north and south bound motorway lanes, was erratic.
‘‘Sometime the signs are flashing but there’s no truck in sight,’’ McGlade said.
Speeding said it only had to be ‘‘a windy day’’ to trigger the warning signs.
Plastic sheeting covering tall loads could come loose and billow up tripping the sensor, Speeding said.
McGlade said a truck accelerating could cause its suspension to rise, elevating a load higher than it really was.
Auckland Mayor Len Brown said after the bridge strike that Penrose overbridge was a continuing hazard and it should be replaced.
Spedding agreed and said the 63-year-old span was ‘‘completely out of date’’ and should be replaced with a higher bridge.
But NZTA said it has no plans to replace the overbridge.
NZTA’s Auckland Highway Manager Brett Gliddon defended Penrose overbridge’s warning system calling it ‘‘extremely robust’’ and saying it ‘‘does not produce false readings’’.
Additional sensors installed two years ago ‘‘validate’’ the main sensor’s warnings and most days ‘‘real’’ height warnings were triggered, he said.
Often warnings were caused by flapping tarpaulins or other flexible items, Gliddon said, but such instances were considered ‘‘genuinely over height’’.
‘‘They often result in the vehicle passing under the bridge without striking it because the items are flattened as they go underneath.’’
As motorways have inconsistent road surface heights, the agency’s Penrose height warning was set to trigger approximately over 4.35 metres, a tolerance that also allowed for suspension bounce and soft trailer covers, Gliddon said.
A new Penrose over-height warning system with extra warnings would be be working by July, he said.
Despite misgivings about Penrose overbridge’s warning system, truckers McGlade and Spedding agreed with transport body Road Transport Forum that final responsibility for checking load heights rested with the driver.
Nationwide civil contracting company Higgins Group, whose truck towed the digger involved in the Penrose crash, has repeatedly refused comment on the incident.
NZTA say their over height warning signs approaching Penrose overbridge work well.