A full replacement of the bridge is proceeding and this work could be completed by the end of next year.
It is also the preferred route for part of a proposed cycleway linking coastal communities north of Dunedin.
One section of the cycleway would link Waikouaiti with Karitāne, but clipping a cycleway on to the side of a 150m rail bridge is not expected to be straightforward.
A feasibility study for the Dunedin Tracks Network Trust has already put the cost of this at about $1 million.
KiwiRail acting chief operations officer Paul Ashton said all elements of the bridge were being replaced.
"Additional piling work would be required were a cycle clip-on to be added to the Waikouaiti bridge, and this design requirement has been shared with the trust looking at the pathway as it considers its options for crossing the river.
"This issue is in its very early stages and KiwiRail has not taken any position on any option."
KiwiRail is supportive in principle of the cycle trail’s development, which could end up connecting Waikouaiti and other communities to Port Chalmers and Dunedin.
A stretch of shared path from Port Chalmers to St Leonards is due to be formally opened on Saturday.
Coastal Communities Cycleway Connection representative Emily Cooper said the clip-on was still the preferred option for the section from Waikouaiti to Karitāne.
"We have yet to go through the detailed design process with KiwiRail," she said.
The trust is working through funding application requirements, consents, easements and approvals for the trail.
It has been broken up into five sections and much of the proposed trail would run alongside railway tracks.
The Main South Line runs from Dunedin to Port Chalmers, then north through Waikouaiti.
A trail would have to meet KiwiRail design and construction specifications.
This would include maintaining a standoff distance of at least 5m between the middle of railway tracks and the trail, the feasibility study noted.
Fencing between the trail and railway would also be needed in places.
KiwiRail has approved in principle the trail sections from Waikouaiti to Karitāne and from Evansdale to Waitati.
