The harbour arterial route project will mean major changes to Anzac Ave, which will become a cul-de-sac from Hanover St north, and a road mainly for walking and cycling.
There will also be changes to Frederick St, which will be expanded to a four-lane road helping to connect northern and southern Dunedin.
The plan included a "gyratory" - a large raised roundabout-style construction crossing the railway lines at the end of Frederick St, and was expected to fundamentally change traffic flows in the city, Dunedin City Council transportation planning manager Don Hill said.
The new arterial route would begin with changes to intersections at each end of Strathallan St, with work due to start this spring, and would extend the harbour end of St Andrew St alongside the railway line north towards Ravensbourne, with a new bridge across the Water of Leith.
If the Awatea St stadium went ahead, it would skirt around the building, before linking with a roundabout on Ravensbourne Rd.
Mr Hill said the changes to the traffic flow would pull traffic away from Andersons Bay Rd, possibly allowing Cumberland St to become two-way, and Crawford St to become a local road with cycleways, servicing the retail sector there.
Traffic coming from the Southern Motorway would use the new route to travel north.
The changes were first mooted in the council's transportation strategy, released in 2006.
More recent design work for aspects like the gyratory and the stadium realignment had resulted in firmer ideas about what they would look like.
"It actually is a very fundamental change to the network," Mr Hill said of the project.
The work would help solve congestion on city roads, and also help deal with expected population and vehicle growth.
Mr Hill said 90% of traffic arriving from the south to the St Andrew St/Anzac Ave intersection turned right on to Anzac Ave, heading north.
"If you think about the population and where people work, they're heading for the hospital, the campus, business - they're all pulled to the north end."
In the south, traffic was expected to take the new route, rather than Andersons Bay Rd and Crawford St, areas of congestion.
"It changes and improves the flows throughout the city. That's why it's a good project."
Traffic on Frederick St would rise significantly with the changed network, he said.
The eastern end would change from two to four lanes, something that would be achieved by removing parking.
Transit New Zealand had signalled it would include that part of Frederick St as part of the state highway.
The final aspect of the project was to create access to the harbourside.
"If you're walking from hotels in the Exchange, you've got the pedestrian overbridge [beside the Railway Station] that's being rebuilt, or the Cumberland St overbridge.
"Long-term we would like access via Rattray St, but we recognise we can't do that with the rail shunting yards there."
But only 10% of rail cargo was going to Dunedin, while 90% was going to Port Chalmers, he said, and in the future, an area suitable for shunting needed to be found closer to the port, something that would release industrial land in the city, as well as allowing access.
Mr Hill said apart from the bridge over the Leith and the gyratory, building the connecting roads on mostly OnTrack land by the railway line was "relatively simple".
The council had an agreement in principle with OnTrack to buy the land, and the company would benefit because tight curves at the Ward St overbridge, which caused damage to rolling stock, could be straightened when the new road was in place.
The council was negotiating with individual landowners for the rest of the land.
Work on the new Leith St bridge and the gyratory would start next year, and take 15 to 18 months to complete, he said.
Another aspect of the project was to move the road near the skateboard park closer to the railway line, and move the skateboard park to where the road was now.
Mr Hill said that would not happen until 2016.
Road facts
Project: The harbour arterial route, a Dunedin City Council project that will fundamentally change traffic flows in the city.
Cost: $34 million, with Land Transport New Zealand expected to pay 65%, the DCC 35%.
Where: Runs from Strathallan St to Ravensbourne Rd.
Why: To improve the efficiency of the inner city roading network.
When: Work on Strathallan St to begin later this year, work further north to begin next year.
