Melbourne's historic Sandridge Bridge could be turned into an "aerial park" similar to New York's famed High Line gardens.

Lord Mayor Robert Doyle has back a proposal to create a tree-lined park on the 178-metre pedestrian and cycle bridge that connects Flinders Street Station to Southbank, but has conceded he is not sure how much it would cost.

The concept of the refurbished Sandridge Bridge. Credit:Melbourne City Council

The Sandridge Bridge was part of the former Port Melbourne rail line - the first passenger railway line in Australia - and was reopened as a pedestrian bridge in 2006 featuring public artwork paying homage to Victoria's migrant history.

The Lord Mayor said the bridge was important but "drab".