Post-war developments in civil engineering owed much to the development of the car and in the 1950s and 60s highways construction boomed.
Halcrow designed one of the early schemes, the Ulster M1 motorway leading south from Belfast. With experience gained this was followed by the Perry Barr Expressway in north Birmingham. Halcrow had full responsibility for the design of the whole route which was to carry Birmingham’s heavy urban and suburban traffic to the M6 motorway.
The section of A34 being developed was originally an overloaded 30ft single carriageway with the single exception of the Birchfield Road Underpass, which had no median strip. It was upgraded to a dual 24 feet carriageway with 22 feet frontage roads on either side and grade separations at important junctions.
The first section completed was the Birchfield Road Underpass, which was opened to traffic in 1962. This was followed by Aston Six-Ways Underpass in 1963 and by the elevated carriageway in Aston High Street in 1967.
A new contract was awarded in 1968 for the Trinity Road Flyover section of the Expressway. It was constructed of precast prestressed concrete box beams 65 feet 10 inches long on reinforced and prestressed concrete cantilever slabs supported by four groups of columns. Each of these columns consists of four reinforced and prestressed concrete legs of varying cross-section, splaying out from a common rectangular base. The base formed the pile cap to a square of four piles extending, with a maximum depth of 128 feet, into the rock and sand foundations below.