The Driftway is a Hawkesbury City Council Road located on the Hawkesbury City Council and Penrith City Council LGA boundary.

BG&E, in partnership with Mott Macdonald and RPS, operating as MRB JV, carried out the detailed design services for Transport for NSW (TfNSW).

The key design features of the proposed upgrade to The Driftway include

• Upgrade of the Londonderry Road and The Driftway intersection to a roundabout, including two southbound lanes through the roundabout for emergency flood evacuation requirements.
• Realignment of 230 metres of The Driftway at its eastern extent to create a four-leg roundabout with Blacktown Road and Racecourse Road.
• Upgrade of intersections with Luxford Road and Reynolds Road to painted channelised right turn T-junctions.
• A new bridge over a tributary of Rickabys Creek (separate TfNSW detailed design).
• A new retaining wall along the northwestern corner of Racecourse Road and Blacktown Road.
• Pavement improvements to 3.6 kilometres of The Driftway, including widening both shoulders from one to 1.5 metres.

To minimise cost, the proposed pavement solution was in-situ stabilisation of 200 millimetres of the existing pavement with a 200 millimetre overlay.

Due to the highly variable existing pavement crossfalls, the road design was carefully prepared to ensure that the use of existing pavement was maximised without adversely impacting the geometric road design solution. This also minimised the extent of full depth pavement widening.

Construction staging featured heavily in the design development and full depth asphalt was proposed to allow temporary traffic loading and temporary ramps to be used.

BG&E was also engaged to undertake site durability investigations of existing culverts with the aim of retaining the existing infrastructure and thereby reducing cost. It was determined that culverts were suitable for retention which enabled further savings to the project and the pavement designs were adapted to suit the low cover of existing culverts.

To enhance safety and eliminate several design concessions, the team lowered the design and posted speeds to align with existing conditions.

Budget and programme were key drivers. To ensure that the road safety outcomes are maximised, a preferred concept was preferred for TfNSW. In order to meet program commitments, the 80% and 100% detailed design phases were shortened.