A mighty road bridge across the famous Firth of Forth in Scotland, built mainly with steel supplied from China, will be open to traffic on Wednesday.

The new bridge is expected to become a new landmark for Scotland, standing alongside a second road bridge and the iconic 19th-century Forth rail bridge which was recently inscribed as a UNESCO World Heritage Site.

Shanghai-based ZPMC (China) was contracted to supply around 75 percent of the high-quality steel needed for the new crossing, Britain's biggest bridge contract so far this century.

The new Queensferry Crossing is the world's longest three-tower cable stayed bridge and also the largest infrastructure project in Scotland in a generation.

Costing 1.75 billion U.S. dollars, the bridge and its approaches stretch for 2.7 km and have taken six years to build.

Scotland's First Minister Nicola Sturgeon has described the design, engineering and construction as amazing and said that, alongside the two other bridges, the crossing will be a tourist attraction and a beautiful addition to the Scottish skyline.

The Scottish government had faced criticism for not sourcing steel for the bridge from Scottish or British suppliers.

But Transport Scotland confirmed that no steel companies from Scotland or the United Kingdom had bid to supply materials for the Queensferry Crossing contract.

More than 15,000 people have worked on the construction site since 2011, clocking up over 18 million hours of work in the process, with thousands more indirectly employed through the project's supply chain.

Around 50,000 people are expected to walk the new bridge this weekend ahead of the official opening on Sept. 4 by Queen Elizabeth II, who opened the first 2.5-km suspension road crossing in 1964.

The Scottish government says the new bridge is expected to lead to a stream of new business looking to acquire land and property in the surrounding areas. It will also help advance tourism opportunities.

A tourism strategy is due to be unveiled later this year which will seek to tap into the three bridges as a unique setting and world-leading visitor destination.

Scottish Economy Secretary Keith Brown, said, "It will be with a real sense of pride that all those involved with this project will witness traffic crossing the bridge this week. The challenges of this location have been well-documented and the real heroes are those who have braved the elements in sometimes horrendous conditions to finish the job."

Project director David Climie said, "I've worked on projects across the globe and I can safely say that this has been one of the most challenging but also the most rewarding."

"Until you've actually been out on the bridge during severe winds it's hard to appreciate the task at hand of delivering such a complex project," he said. "Experts from across the globe have marvelled at this achievement."