Construction of the M4 Widening, WestConnex Stage 1A

The M4 Widening project comprised the first stage in the delivery of WestConnex. It involved the widening and upgrading of approximately 7.5 kilometres of the M4 Motorway (M4) between Pitt Street, Parramatta and Homebush Bay Drive, Homebush. The project was opened to traffic in July 2017, in line with the contract program, and is considered one of the most difficult “Brown Field” pavement projects to be undertaken in New South Wales. During construction, the project team overcame site constraints and conditions not typically encountered on motorway pavement projects. The project required the construction of multiple varieties of pavements to match the largely unknown, existing pavement models constructed over the previous 50 years, the construction of which was still based on conformance to the R82/R83 specifications. This presented a massive challenge for the project team. Further, site constraints such as the size of work areas, small road closure windows, restrictive out of hours conditions, and access to site via one of Australia’s busiest and most congested motorways conspired to add additional levels of difficulty to an already complex and technically challenging project. The solutions implemented to combat these constraints were many and varied, however an adaptive and dynamic design and construct process was by far the most effective. Considering the experiences from the M4 Widening, this paper will provide insight and learnings to lay the groundwork for a practical design and construction guide for future “Brown Field” pavement projects.