Editor's note: This story has been updated to clarify the difference between Texas Central's Sept. 13 announcement about a design-build contract with Salini Impregilo and an October 2018 announcement about a limited-notice-to-proceed agreement with Salini Impregilo. 

Days after being granted the Rule of Particular Applicability by the Federal Railway Administration, Texas Central announced Sept. 13 having signed a design-build agreement with civil engineering firms Salini Impregilo and Lane Construction Company to build the high-speed train. Lane Construction is the U.S. subsidiary of Salini.

According to a Sept. 13 news release from Texas Central, the agreement means Salini-Lane will design and construct an estimated $14 billion of civil works, which includes the viaduct—which elevates the track across land—and embankment sections along the Houston-to-Dallas route, the track system, and all buildings and services that will house maintenance and other rail system equipment along the route.

"This agreement brings us one step closer to beginning construction of the civil infrastructure segments of the project," Texas Central CEO Carlos Aguilar said in the release. "Salini-Lane's unmatched track record with rail infrastructure, and very specifically its world-class high-speed rail expertise across the globe, will be central to the completion of America's first end-to-end high-speed rail system."

Texas Central announced in October 2018 a limited-notice-to-proceed agreement had been made with Salini Impregilo, since which time Salini-Lane has continued its design and planning efforts for the rail infrastructure, according to a statement from Texas Central.

"Since last year’s Limited Notice to Proceed agreement, Salini-Lane has focused on front-end engineering, design and planning of the train’s civil infrastructure. Services included optimizing execution plans, strategies and logistics, as well as performing analysis to develop and optimize construction costs and schedule estimates. That work helped to develop this design-build contract [announced Sept. 13]," a statement on Texas Central's website reads.

According to the release, Salini has built more than 4,000 miles of rail infrastructure spanning 50 countries.

"This inclusion in bringing high-speed train service to Texas and America, through leading the project's design and construction, is an invaluable experience," said Pietro Salini, CEO of the Salini Impregilo Group in the release.

Texas Central's high-speed train is estimated to be a $20 billion investment when completed, according to the release. The high-speed train will connect Dallas and Houston, giving riders a 90-minute trip with a third stop in the Brazos Valley.

"With increasing congestion on our highways and airways, it is important that we look at alternative modes of transportation," said Robin Kemper, president of the American Society of Civil Engineers, in the release.