Public transport users should check bus timetables for changes as construction work begins on the O-Bahn bus extension project in Adelaide.

During the next six weeks, new bus lanes will be installed in the middle of Hackney Road.

The Hackney Road bridge will be widened and the tunnels at the North Terrace end of the project will start to be built over the next few months.

The project is expected to be completed at the end of 2017.

The Department of Planning, Transport and Infrastructure website said the project aimed to improve travel times and reliability.

Transport Minister Stephen Mullighan said there would be traffic disruptions.

"Works are being scheduled to try and stay out of peak periods and to focus works outside of the festival season and take advantage of the night and weekend work," he said.

"There will be some lane and speed restrictions."

Bus commuters have been told to check the Adelaide Metre website.

"There will be some temporary changes to the O-Bahn and 281 bus timetables," Mr Mullighan said.

"This will be an important project for not just to improve the O-Bahn bus service but also the ring route for the city, particularly along Hackney Road which is used by 40,000 motorists."