Network Rail has begun the process of appointing a main contractor to design and build the new Forth Bridge Experience.
Potential partners are being asked to submit their interest before Network Rail shortlists firms to tender for the project later in the summer.
A main contractor is expected to be appointed by the end of 2020 with work on-site commencing in 2021.
Plans for the Forth Bridge visitor centre and bridge walk experience gained planning permission from City of Edinburgh Council earlier this year.
Network Rail plans to create a new hub at the iconic bridge where the public will be able to access the world-famous structure and explore its heritage as well as the outstanding views from 367 ft (110m) above sea level.
The project will see construction of a bridge walk and reception centre on the south side of the UNESCO World Heritage site, which will be used for preparing those heading out on the bridge walk as well as providing an access point to the structure.
Groups of upto15 people will put on safety harnesses before being led out onto the bridge’s south cantilever, walking up to a viewing point at the top using walkways built into the structure.
Between three and four groups an hour will be permitted on the bridge, with each tour expected to last around two and a half hours.
It is estimated the bridge walk experience could attract around 85,000 visitors, bringing real benefits to the local community and creating around 35-40 jobs.
Longer-term plans to create visitor facilities at the north end of the bridge are also under development and could see future access to the top of the north cantilever, via a lift.
Alan Ross, Network Rail Scotland’s director of engineering and asset management, said: “The bridge walk experience will offer the public a unique chance to explore this world-famous structure and bring a real economic boost to the local economy.
“Appointing a main contractor to help us deliver this project will be a major milestone in creating this new attraction.
“This will be a challenging and exciting project for any company to work on and we look forward to working with the wider construction industry to develop a shortlist to tender.”