It would start at Peter Johnstone Park in Mosgiel and run by the Silver Stream and then the Taieri River, using the Queen’s Chain to Outram, project advocate Colin Brown said.
It would feature a suspension bridge across the Taieri River, Mr Brown said.
However, the indicative route is subject to negotiations with landowners, lessees and the Otago Regional Council.
The council would need to be satisfied the off-road trail would not compromise flood-protection infrastructure.
Mr Brown is due to make a presentation to the Dunedin City Council this week, pitching for funding for the first section of the trail.
It is envisaged the full trail would run from Mosgiel to Waihola, linking up with the Clutha Gold Cycle Trail.
It would also connect with the planned trail between Mosgiel and Dunedin.
Should it all come together, cyclists will eventually be able to access the popular Clutha and Central Otago trails from Dunedin while staying clear of highway traffic.
The Taieri Cycle Trail Group submission to the city council described the Mosgiel to Outram section as 14km in length on flat terrain, making cycling off-road a viable alternative to using cars.
It could improve access to the Outram Glen picnic and swimming area and the new Mosgiel pool, which is due to open soon.
The Dunedin Tunnels Trail Trust, which is behind the proposed trail from Mosgiel to Dunedin featuring two disused railway tunnels, has its own submission to the city council.
The trust was pleased to see tenders being called for repairs to the Chain Hills tunnel, but noted the tunnels trail had been "continually delayed and de-prioritised".
"As the cycleway network around Otago develops and expands, bringing with it tourism and the all-important local community benefits, both economically and health-wise, Dunedin has remained isolated."
The Mosgiel-Taieri Community Board supports extending the Clutha Gold Cycle Trail from Waihola to Outram and Mosgiel.
"If successfully established, this cycle trail will bring immense benefit to the Taieri from the economic activity fuelled by ever-increasing numbers of cycle tourists," the board said in its submission.
"Similarly, the planned tunnel trail linking Mosgiel to Dunedin will be an invaluable tourist and recreational trail which also offers a genuine zero carbon commuting option between the two centres.
"The repurposing of two historic rail tunnels to provide a safe, usable walking and cycling link between Mosgiel and Dunedin creates an exciting new option for accessing our community from Dunedin."
Seventy-year-old cyclist Ant Wither issued a plea to the city council to keep on developing the cycle network.
"I live in Mosgiel and there is no dedicated biking, apart from a painted line on Factory Rd.
"It would be wonderful to ... bike to Outram (ultimately Waihola) off-road and also into Dunedin via the tunnels."
