Chicago has accepted bids from four private companies to design, build, finance, operate, and maintain a high-speed train predicted to cut travel time down to 20 minutes between downtown and O’Hare Airport.

Chicago Mayor Rahm Emanuel stated, “Four visionary groups have stepped forward because they see what we see—a connected Chicago is a stronger Chicago.”

Dubbed the O’Hare Express, this long-discussed endeavor is forecasted to cost billions of dollars, which is raising concern among Chicago’s citizens. However, officials have been quick to dispel any notion that these expenses will be passed along to tax payers as the project is slated to be entirely financed by private investors.

Due to the fact that CTA’s Blue Lines train already connects O’Hare to the city, the project has garnished criticism from some groups. Yet officials have countered, citing statistics estimating that the number of commuters traveling via the current infrastructure, will increase from 20,000 to 35,000 passengers over the next three decades, drastically exceeding current capacity.

California-based tunneling firm, The Boring Company, is situated at the forefront of the contending bidders as the most viable and defined solution at this point. It’s anticipated that Owner Elon Musk, Tesla and SpaceX founder, will propose high-velocity electromagnetic pods or sleds, much like the sled system he recommended for Los Angeles last month. To reduce construction costs, The Boring Company will likely employ experimental drilling technology with narrower tunnel diameters for more rapid excavation.

Even though there is still much to finalize, construction is expected to commence within the next three years. Mayor Emanuel recently tweeted that the express route would “give Chicagoans and visitors to our great city more options, faster travel time, and build on Chicago’s competitive advantage as a global hub of tourism, transportation and trade.”