Adelaide Hills interchange upgrades motoring ahead

Wednesday 18 February 2026

Road in the Adelaide Hills

Works are now underway on the Australian and South Australian Governments’ upgraded interchanges at Mount Barker and Verdun, paving the way for easier and safer connections between the South Eastern Freeway and the Adelaide Hills.

Site preparations are underway at both sites, with night works construction on the South Eastern Freeway commencing at Verdun from Sunday February 22 and at Mount Barker from March 1.

Approximately 31,000 vehicles travel along the Freeway between the Mount Barker and Verdun interchanges each day, with 46,000 vehicles travelling from Verdun into the city.

Approximately 31,200 vehicles travel across the Mount Barker interchange which is subject to significant traffic congestion and queuing. There were 43 crashes reported between 2019 and 2023, and 11 reported crashes at the Verdun Interchange during the same period.

The new interchanges will have increased capacity, helping to reduce bottlenecks, driver frustration and the risk of crashes and will better accommodate existing and projected growth in the rapidly expanding Mount Barker and Adelaide Hills area.

Better traffic flow will help improve access and response times for emergency vehicles and the interchanges will also be easier for tourists to navigate.

Construction on the interchanges follows extensive community consultation and information sessions about the transport infrastructure investments in the hills attended by almost 150 people.

The Mount Barker Interchange will include a new three-lane bridge across the South Eastern Freeway for northbound traffic and the conversion of the existing bridge to accommodate three lanes of southbound traffic.

Constructing the bridge for the Mount Barker Interchange will require the installation of 12 super-T girders, each weighing 85 tonnes.

An estimated 20,000 tonnes of asphalt will be laid and 500 metres of new underground pit and pipe drainage will be installed.

New traffic signals and smart lighting at the interchange will improve access and safety. A new shared use path will improve pedestrian and cyclist connections across the Freeway, and a new priority bus lane will help keep people moving.

The existing Verdun Interchange will be upgraded to a full interchange, allowing access to and from the South Eastern Freeway in all directions to improve traffic flow and safety while providing a better connection to surrounding towns.

Currently, at the Verdun Interchange there is no exit ramp for motorists driving from Mount Barker to Hahndorf, and no entry ramps for eastbound motorists; meaning motorists wanting to travel between Hahndorf and Mount Barker can’t easily access the freeway.

The new full interchange will feature a new eastbound entry ramp towards Mount Barker, and a new westbound exit ramp, which will cross under the existing westbound entry ramp and connect with a new roundabout at the junction with Mount Barker Road and Silver Road.

The new bridge over the westbound Freeway exit underpass will be 13.45 metres in length with a deck width of seven metres, supported by 26 concrete piles and 12 bridge planks.

Construction of the new Verdun Interchange will include more than 20,000 tonnes of asphalt, 86 tonnes of concrete capping beams, over 13,000 tonnes of granular pavement and 2.25 kilometres of new stormwater pipes.

The total project cost to upgrade the Mount Barker and Verdun interchanges is $150 million, with the Australian Government committing $120 million and the South Australian Government contributing $30 million.

South Australian company Bardavcol Pty Ltd will deliver the upgrade of the Mount Barker Interchange, while a joint venture between BMD Constructions Pty Ltd and Leed Engineering and Construction Pty Ltd will undertake the Verdun Interchange Upgrade.

Construction of both interchanges is expected to support approximately 260 full-time equivalent jobs per year during the construction period, with both interchanges expected to be open to traffic in late 2027.

These projects complement the work currently underway on the $40 million upgrade of the Mount Barker roundabout at the intersection of Adelaide Road, Alexandrina Road, Wellington Road and Flaxley Road.