After nearly two years of traffic disruptions and delays, and months more of debate and dispute, Adelaide's new O-Bahn tunnel is expected to open to public metro buses on Monday.

The $160 million project was officially unveiled today, with locals given the chance to walk the length of the 670-metre tunnel from Hackney Road to Grenfell Street.

The tunnel is intended to ease congestion and reduce daily travel times for passengers heading to and from the north-eastern suburbs, and has been delivered "on time and on budget", according to the SA Government.

Wheelchair users have raised concerns about evacuation procedures in the tunnel for people with disabilities — criticisms which were rejected by Transport Minister Stephen Mullighan.

But Mr Mullighan stopped short of guaranteeing the first services through the tunnel would be on Monday morning, adding that final safety testing had to be carried out first.

"We've just got to make sure that after having so many thousands of people coming through the tunnel today, we do a full inspection, a check and one more test of all of the safety and security systems within the tunnel," he said.

"That'll give us the confidence we can start running services."

The 670-metre tunnel stretches from Grenfell Street to Hackney Road. ( ABC News: Tom Fedorowytsch )

Only a handful of routes will be passing through the tunnel when services start tomorrow, but every O-Bahn bus should be using the tunnel by next weekend, the Government said.

Once fully operational, more than 30,000 passengers are expected to use the tunnel each week day.

Mr Mullighan said the first few hours of its operation would help transport authorities get to grips with any teething problems.

"All of the systems that have been installed ... will be under intense scrutiny during those first services," he said.

"We've got to make sure that we've got the calibration of the traffic lights and the traffic systems correct."

Drivers 'unclear about emergency procedures'

Concerns about emergency procedures inside the tunnel have been rejected by the Transport Minister. ( ABC News: Tom Fedorowytsch )

Dignity Party MP Kelly Vincent, who was among those inspecting the tunnel this morning, was concerned passengers with disabilities were not properly considered during the planning.

"We've been contacted by bus drivers who say they're not clear on what the evacuation procedures are," she said.

"If there is a fire or another emergency and they have someone who is a wheelchair user or uses a gopher or other mobility aid, they are concerned about potentially not being able to deploy the ramps because the footpath is ... very narrow."

But Mr Mullighan said he had been advised safety testing took wheelchair users into consideration.

"They did test getting people off those buses who do have mobility issues, who were in wheelchairs," he said.

David Pisoni points out a dip in the road caused by buses on Grenfell Street. ( ABC News: Tom Fedorowytsch )

Opposition transport spokesman David Pisoni said the O-Bahn project should have been accompanied by improvements to Grenfell and Currie streets.

He said the number of buses along the thoroughfare meant the road needed better maintenance.

"What's underneath the bitumen is what needs to be repaired. It's not good enough simply to patch the bitumen every time we see a pothole or a dip in the road caused by the buses," Mr Pisoni said.

The Government said the tunnel project had supported 450 jobs, generated $94 million worth of contracts and used about 2,000 tonnes of Whyalla steel.