A1(M) Birtley By-pass

A 2.5 mile section of dual three-lane carriageway costing £2.3 million. Constructed between July 1968 and April 1970 by Robert McGregor & Sons Ltd. On completion this was the first dual three-lane motorway north of the M1. The scheme was built on the same alignment as the existing Trunk Road A1 dual carriageway by-pass, built in the 1930s. The contract included five bridges, one over a railway. The bridges had spread footings. Four had pre-cast pre-stressed beams. One bridge had steel I beams and was the longest single-span bridge to have been designed by the NERCU (North East Road Construction Unit) Durham Sub-Unit. The span was 150 feet and had a skew of 33 degrees. Each of the 8 beams weighed 30 tons. This bridge carried the north carriageway over the southbound carriageway of the A1(M), being the future link road to the Tyne Tunnel. Two mine shafts were found (12 were shown on the contract drawings, all disused for nearly 100 years). The in-filled shafts were capped by concrete slabs 2 feet thick.