Tinwald Viaduct in Ashburton one of the most hit in the country

The Tinwald Viaduct shows the signs of numerous incidents where oversized vehicles have hit the bridge, making it the second-most hit bridge in the country in the last two years. Photo / LDR / Jonathan Leask

Jonathan Leask, Local Democracy Reporter

Three times a year a driver will crash into the Tinwald viaduct - which authorities say is clearly signposted.

The viaduct on Melcombe St in Tinwald, the suburb on the southern end of Ashburton, passes under the railway line and has a height restriction of 2.39m but three times in each of the last three years it has been hit by oversized vehicles.

KiwiRail said it is the second most-hit rail bridge in the country over the last two years.

The most hit bridge is in Taumarunui which has had 34 bridge strikes since 2004.

A KiwiRail spokesman said the incidents are mostly camper vans or small vans, not commercial trucks “who probably know to avoid the bridge and are more aware of their vehicle height and height restrictions”.

The spokesman said the bridge’s height restriction has adequate signage and advanced warning signs which are the responsibility of the local roading authority.

Ashburton District Council infrastructure and open spaces group manager, Neil McCann, said the existing warning signs are clear but the council and Waka Kotahi NZ Transport Agency are looking at ways to improve road safety around the Tinwald viaduct.

”We plan to increase the size of the signage across the top of the viaduct arch to make it more visible,” McCann said.

“A new sign informing of the height restriction is proposed to be installed on Melcombe Street for those approaching the viaduct from the west as part of Waka Kotahi’s State Highway 1 Tinwald Corridor Improvements project.”

The warning signs for the height restriction at the Tinwald Viaduct are deemed adequate but further safety improvements are being investigated. Photo / LDR / Jonathan Leask

Whether any further signage pointing to the height restriction will be installed on SH1 is a decision for Waka Kotahi McCann said.”

One factor we believe might be contributing to issues is that GPS navigation may be directing drivers to Melcombe St and the viaduct to avoid congestion on SH1.

”We have reached out to a commonly-used mapping service and, while it is outside of the council’s direct control, we hope that the height restriction will be noted on that navigation service in the future.”

When a rail bridge gets hit the KiwiRail spokesman said the driver should call the 0800 number which is on each of KiwiRail’s bridges with the bridge number and line quoted on it.

Once train control, which is monitored 24/7, receives the call they contact the local structures inspector and will stop all trains from going over the bridge.

Once KiwiRail staff have inspected the bridge for safety, train control can allow trains to go over the bridge the spokesman said.

An engineer’s report is also completed by a third party at a later date to confirm if any repairs are required, the spokesman said.

Two-way access

In the latest plans for the Tinwald Corridor Upgrade, due to start later this year, the Melcombe Street viaduct will remain open to two-way traffic. It had been proposed to be limited to left-out only onto SH1 and Waka Kotahi director of regional relationships, James Caygill, said the change was made following public consultation but it will be monitored “to maintain that works”.