A group of volunteers has been formed to carry out the work, and has started raising funds and looking for other volunteers to help.
A recent engineering report calculated restoring the bridge, closed for at least 10 years because it was unsafe, could cost between $144,000 and $286,000, depending on its condition.
That would only be known once rotten decking and timbers were removed.
But Railway Bridge Restoration Group member Rex Stringer said the cost would be reduced by volunteer labour and Australian hardwood timber already stockpiled from demolition of such things as bridges.
The bridge is in a decrepit state, fenced off at each end and an eyesore.
However, an engineer's report indicated it was structurally sound, despite its appearance.
Wansbeck St has been extended to a roundabout at the end of Holmes Wharf at the harbour.
The road extension is being used by more people to access the harbour, including tourists.
Mr Stringer said the restoration group had already raised about $3500 towards the project, and was about to apply to larger grants funders.
The timber it had stockpiled was suitable for the bridge and worth about $10,000.
The group had the support of other organisations to restore the bridge, but was also looking for volunteers, with or without skills, to help.
"We are aiming to have the work done at least by the end of next year," he said.
The bridge provided pedestrian access to and from Friendly Bay over railway lines used by goods trains to get to the railways goods yard and shed, before it was closed.
The track is now used by Oamaru Steam and Rail on its weekend runs from its Itchen St station to the Red Sheds at the harbour.
