The newly installed Pedler Creek Bridge at Seaford Heights has partially opened to traffic for the first time, improving the journey for the nearly 17,000 motorists who travel along Main South Rd every day.

Two lanes on the bridge's eastern side opened on Friday 13 October, providing one lane for traffic in each direction.

Work is continuing on the western lanes, with the bridge expected to fully open to motorists by the end of the year.

The structure, on Main South Rd, also includes a shared-use path which will open when the four lanes are operational, to help keep cyclists and pedestrians safe.

The new bridge is 161m long and almost 24m wide. It is supported by 50 super-T support beams, each around 35m long and weighing up to 64 tonnes.

Demolition of the old bridge will start in the coming weeks and is expected to take about eight weeks to complete.

Meanwhile, a new overpass opened last month on Main South Rd at Tatachilla.

The overpass, located at the intersection of Tatachilla and Maslin Beach roads, is supported by nine super-T girders, each 37.5m long and weighing 81.7 tonnes.

Both projects are part of the 9.8km Main South Rd duplication project, from Griffiths Drive, Seaford, to Port Rd, Aldinga, expected to be completed in early 2024.

The South Australian and Australian governments have jointly committed a total of $685 million to fund the Main South Rd and Victor Harbor Rd duplication projects.

The projects have supported around 945 full-time jobs each year during construction.

Once completed, it will result in safer and faster journeys for motorists and provide a vital boost for local tourism.