The 42km line from Dallas Fort Worth Airport (DFW Airport) and Shiloh Road in Plano will connect northern areas of Tarrant, Dallas, and Collin counties along interstate highway 635, one of the most congested road corridors in Texas.

The double-track line will serve 10 stations in the cities of Grapevine, Coppell, Dallas, Carrollton, Addison, Richardson and Plano, including interchanges with the Dart light rail Orange, Green and Red lines, the Tex Rail commuter line to Fort Worth, and local bus services.

Two stations - Coit and Preston Road - have been omitted from the plan approved by the Dart board, shaving $US 30.3m off the cost of the project, which is now budgeted at $US 1.1bn.

Services will be operated by a fleet of at least seven DMUs, which will be maintained at a purpose-built depot.

The line is expected to open and will operate seven-days-a-week with trains running at 30-minute headways in the peak and hourly off-peak. The 2040 operating plan assumes services will be stepped up to 20-minute headways in the longer-term.

Dart plans to finance the project with the aid of a $US 908m federal loan via the Railroad Rehabilitation and Improvement Financing (RRIF) programme. The remaining funds would be drawn from a combination of other federal, regional and local sources.

Annual operating and maintenance costs are estimated to be around $US 17.8m.

The Cotton Belt Corridor was identified as a priority scheme in the Dart 2030 Transit System Plan, which was published in 2006. In 2016, Dart’s 20-year financial plan brought forward the completion date for the project to 2022.

A 45-day public consultation on the draft environmental impact statement for the project was completed in June.