Case Study: M1 Pacific Motorway Widening, Tuggerah to Doyalson

Lindsay Dynan recently partnered with CPB Contractors and RMS to deliver an extensive motorway widening project for the M1 Pacific Motorway between Tuggerah and Doyalson.

The M1 Pacific Motorway is a critical link in the National Land Transport Network and part of the Sydney to Brisbane corridor, one of the busiest transport corridors in Australia. The project involved widening a 12km section of motorway between the Tuggerah and Doyalson interchanges from two lanes to three lanes in each direction. This scope of works was inclusive of two grade-separated interchanges and two service centres, all of which required upgrade works.

Challenges

The complexity of the project was due primarily to the requirement for maintaining two lanes of uninterrupted through traffic in both directions at 80km/h. The construction methodology adopted by the successful contractor, CPB Contractors, had to ensure that this uninterrupted traffic flow was achieved for both carriageways at all times throughout the construction staging process, with the exception of small windows of night works where temporary lane closures could be implemented for several hours at a time.

The construction staging methodologies were conceptually designed during the tender phase, however large portions of these designs were found to be unviable or impractical once inspected in detail, requiring that alternative staging options be developed to find viable and efficient solutions. Minimising temporary pavement was a key driver for the contractor, which led to innovative options being adopted in the form of temporary asphalt overlays on existing pavements, and localised milling of existing pavements to achieve temporary design levels.

Drainage and aquaplaning issues were a key focus throughout the project, and Lindsay Dynan undertook extensive calculations in order to understand the existing issues and provide the most efficient solutions. Extensive correspondence with RMS was required to ensure that the best solutions for the project were approved and implemented.

Lindsay Dynan’s expertise

Lindsay Dynan provided construction staging design for the M1 project, and these designs were submitted to Roads & Maritime (RMS), NSW Traffic Management Centre (TMC) and an independent Road Safety Auditor for approval. In total, across all construction stages covered by Lindsay Dynan, approximately 30km of motorway carriageway and 36 individual interchange ramps were designed.

The key features of Lindsay Dynan’s work on the M1 Pacific Motorway widening included:

• Detailed geometric road design in accordance with Austroads Standards, RMS Supplements and project specific requirements,
• Drainage design and aquaplaning checks in accordance with Austroads Standards and Australian Rainfall & Runoff guidelines,
• Design to suit the RMS Safety Barrier Specifications for temporary works and the RMS Traffic Control at Work Sites Manual, and
• Preparation of Safety-in-Design assessments and risk assessments to support proposed departures from standards.

Outcomes

Lindsay Dynan was able to help realise time and cost efficiencies for the project by developing sub-stages that separated the scope into smaller work zones, allowing for earlier access. Solutions involving contraflow and bifurcations were developed to address constraints on the horizontal geometry formed by the existing corridor. Bespoke drainage solutions were developed and supported by detailed calculations to help avoid large quantities of subsurface drainage infrastructure.

“The recipe for success was simple and one that is fundamental to our core values – deliver high quality accurate designs, deliver on time, and create an enjoyable team environment that fosters genuine relationships” – Tim Walton, Transport Infrastructure Lead, Lindsay Dynan