NZTA implements $1.3m warning system to prevent trucks ploughing into Penrose overbridge

The new system involves a series of three warnings for overheight vehicles approaching the Penrose overbridge.

Truck drivers heading down Auckland's Southern Motorway will now receive a trio of warnings if their vehicle is at risk of ploughing into one of the lowest and most frequently hit overbridges on the highway at Penrose.

The installation of the $1.3m system, including six new electric signs, was completed by the New Zealand Transport Agency [NZTA] this week and officially switched on overnight on Thursday.

It comes almost four months after a crash, on May 9, when a Higgins driver overestimated the Penrose bridge height and ploughed into it, causing the digger he was hauling to topple and block two of the three southbound lanes on the Southern Motorway.

It's hoped the new system will help prevent another repeat of the incident which led to hours of traffic chaos on the city's motorways.

It works by giving drivers repeated visual warnings if sensors on either side of the motorway deem a vehicle too tall.

In the first instance two warnings would be issued, prior to a last opportunity to leave the motorway.

NZTA Auckland highway manager Brett Gliddon said those that don't make the exit will be given a third and final warning to pull over or stop.

"It is a very clear warning that evasive action is needed, it will be very difficult to miss or ignore.

"Bridge strikes cause delays that can affect many road users, creating disruption and financial losses to drivers and businesses."

The agency was still seeking compensation from Higgins over damages to the bridge from the May accident, the details of which were still confidential.

NZTA's structural inspection report released to the Herald under the Official Information Act showed the strike's impact caused concrete to come loose from the structure with other visible vertical cracks and distorted steel armour plates.

Truck driver Graham John Kennett, 65, has also been charged with dangerous driving over the crash. He pleaded not guilty at the Auckland District Court in June and is due to reappear in court on September 14.

The charge comes with a maximum disqualification period from driving of six months and is also punishable by a term of imprisonment of up to three months and a fine of up to $4500.

Since 2008 there have been 39 incidents on the Penrose overbridge, 37 per cent of the total number of strikes, 106, across all of the bridges on Auckland's highways.

This year alone the Penrose bridge has been hit four times - with nine strikes at other bridges on the city's motorways.

According to the NZTA the bridge, which has a clearance height of 4.57m, was built in 1952 and had its underside reinforced with steel due to the frequent bridge strikes. The maximum height for trucks travelling on this part of the motorway is 4.25m.

An agency spokeswoman estimated the total cost of bridge-strike damage across the whole of the city network was around $203,000 over the past seven years.

Only one at the Penrose overbridge, on January 29, 2015, was deemed severe enough for the agency to recoup costs of $31,120 from the company responsible, Tracta Tranz.

Bridge strikes

2016 [to date]: 13 strikes including 4 at Penrose
2015: 8 strikes including 4 at Penrose
2014: 7 strikes, none at Penrose
2013: 14 strikes including 6 at Penrose
2012: 16 strikes including 7 at Penrose
2011: 7 strikes including 3 at Penrose
2010: 14 strikes including 5 at Penrose
2009: 17 strikes including 6 at Penrose
2008: 10 strikes including 4 at Penrose

Strikes at the Penrose overbridge accounted for 37 per cent of all bridge strikes on Auckland's Highways

As well as the new system, NZTA is launching an educational initiative aimed at truck drivers.