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“Hidden queue” sign Rakaia rail overbridge SH1, Mid-Canterbury, to warn drivers to slow down


Mid-Canterbury’s Rakaia rail overbridge on State Highway 1, just north of the 1.75 km Rakaia River Bridge, is getting an extra safety feature to warn drivers of traffic queued ahead but out of sight.

Hidden queue sign

The rail overbridge and the much longer, nearby Rakaia River bridge, are key links on the journey along the South Island’s East Coast.

Any vehicle crashes on the Rakaia River main bridge or the overbridge can create delays and lengthy detours, says Transport Agency System Manager Pete Connors.

Vehicles carrying wide loads are also unable to safely pass other traffic on the Rakaia River bridge, requiring the bridge to be closed temporarily in one direction, stopping traffic at the other end, and slowing traffic behind the wide load.

“Queued vehicles on the Christchurch (north) side of the Rakaia River bridge cannot be seen by drivers heading south due to the angle and shape of the overbridge and its high concrete sides,” says Mr Connors.

“This can lead to a dangerous situation where nose-to-tail crashes occur. The most recent was in December last year, which caused a truck to jack-knife closing the highway for about 12 hours, including the busy afternoon and evening traffic. Both the main bridge and the overbridge are relatively narrow, with little room for error by drivers of larger vehicles.

“Given the detour route via the Rakaia Gorge is 96km, adding well over an hour to the journey, we are keen to minimise these events.”

Transport Agency contractors are installing the first electronic “Hidden Queue” sign this week north of the rail overbridge. These bright signs give drivers early warning of traffic ahead but out of sight, so they can slow down.

“The Rakaia River bridge links a large agricultural area, so agricultural vehicles (mowers, harvesters, balers, grain-elevators, tractors) cross it regularly at slow speeds, which is another reason for other drivers to be aware they need to slow down as they approach from the rail overbridge,” says Mr Connors.

“The warning system is activated by slow, south-bound vehicles approaching the Rakaia River bridge. The sign will activate, warning drivers that there could be a hidden queue of traffic ahead, or even slow vehicles which require them to change gear in plenty of time and slow down.”

The signs cost around $40,000 and operate on solar power.