DALLAS - The latest plans for high-speed rail service in North Texas call for slower trains through the Dallas-Fort Worth region and would include a station near the main airport.

The proposal would bring passengers from downtown Fort Worth to Arlington along the Interstate 30 corridor, then extend near Dallas/Fort Worth International Airport. Service would proceed to downtown Dallas.

Top speeds would be around 125 mph, well below the 220 mph the trains are capable of traveling. Short distances between stations and the serpentine nature of the tracks are primary reasons for the slower speeds. The line would follow the local Trinity Railway Express commuter line. The TRE would continue operating on its tracks and a second set of tracks would be built nearby for the bullet trains.

The new route would make high-speed rail accessible to more people in North Texas, a region of about 7 million people that's expected to grow to 10.7 million by 2040.

Transportation planners estimate at $4 billion the cost of the line between Fort Worth and Dallas.

A panel known as the Commission for High-Speed Rail in the Dallas/Fort Worth Region was established nearly two years ago by the Texas Department of Transportation after private investors announced they wanted to build a 220-mile rail line from Houston to Dallas with no public funding.

That line is tentatively scheduled to open by 2022, but construction can't begin until an environmental study is complete.

Because the investors looked to connect only Houston and Dallas, the commission was set up partly to ensure that cities such as Fort Worth also have a station.

Municipal and state officials are considering ways to expand the service to include Austin, San Antonio and other cities. There's even interest in extending the lines north to Oklahoma City and south to Monterrey, Mexico, although that would likely take years to materialize.