Three big players have come together for a joint venture which should see them deliver a seven-year road asset management project for Syney's South Zone.

Leighton Contractors Pty Ltd, Boral Construction Materials and Amey have joined forces to secure the contract worth around $100 million per year.

A statement from Leighton Holdings said the Stewardship Maintenance Contract from Roads and Maritime Services New South Wales was one of the largest of its kind in the southern hemisphere.

The successful contractors will now be tasked with improving maintenance services, including network operations support, operational asset management and project management, across the region's road network.

Network improvements will reportedly include a number of freight and commuter routes to Sydney Airport and Port Botany, as well as covering 2,000 kilometres of roads, 237 bridges and eight tunnels within boundaries from the south of metropolitan Sydney to the Sutherland National Park.

Leighton Holdings will receive $300 million for its part in the project, according to chief executive officer Hamish Tyrwhitt.

“We are pleased to be playing a major role supporting RMS in operating and maintaining the New South Wales road transport network, benefiting the state’s economy and community,” Mr Tyrwhitt said.