One of the country's biggest cranes has rolled on to the Bingley relief road to lift the final beams of an enormous low-level bridge into place.

The 800-tonne vehicle yesterday began to lift the last 15 beams, weighing 36 tonnes each, into place at the South Bog. Workers had the added complication of avoiding two main water pipes which run under the £2.5 million structure.

"The work required great precision because there isonly a very small amount of clearance," said engineer Paul Gott of construction firm Amec.

The bridge's arches will allow the bog's water to flow underneath to maintain its hydrology.

Rare wetland plants growing in the path of the £47.9 million three-mile road, which is due to be completed by autumn, were transported to other areas of the bog before work began.

The last 300 tonnes of concrete at the £5.5 million Cottingley viaduct over the River Aire will be poured at the end of the week, completing the flow of the road.

Highways Agency project manager Peter Scally said: "The contractors have made good progress so far despite some very wet weather at the end of last year."

The final relief road public exhibition will be held at Bingley arts centre, in Main Street, tomorrow, from 8am to 8pm.

Aerial photographs of the route will be on display alongside art by Bingley artist Jane Fielder and local children.