Minister for Regional Transport and Roads Paul Toole said the project had the potential to drive new opportunities across the state.

"This section of railway has not been used for more than a decade, and for its reactivation to be viable, it will need to be able to meet the needs of today's freight trains of 25-tonne axle loadings with speeds up to 80 kilometres per hour," Mr Toole said.

"More than 450 bridges and culverts, 100 level crossings and 179 kilometres of track will require some level of upgrade and replacement. On top of that, we also need to examine the condition of other associated infrastructure, such as tunnels, stations, communication huts and amenity buildings.

"The Cowra Lines has the potential to be economically viable when freight capacity on the Main West is constrained in the future. Having conducted a rail feasibility study on the corridor last year, calls for tender to develop a concept design moves us one step closer to determining a closer project delivery cost."

Member for Cootamundra Steph Cooke said this next stage of design work would help determine whether the Cowra Lines could progress to construction phase.

"Undertaking this high level design now, will speed up work on any future reactivation of the line," Ms Cooke said.

"Some of the features of the line, like the heritage-listed Cowra Rail Bridge and Carcoar Tunnel, are more than 130-years-old and will need special attention to ensure they are both strong enough and provide the clearances needed for freight operations into the future."

Through the Fixing Country Rail program, the successful tender will be expected to complete the required work and provide a report which Transport for NSW will review before advising the NSW Government on future options.