The Dallas Morning News/David Woo

Daniel Acosta watches as his co-workers unload 1,600-foot lengths of steel Tuesday to build the A-train, a passenger rail line that will connect Carrollton and Denton.

LEWISVILLE — Preparations for the A-train rail line — Denton County’s long-awaited foray into commuter rail — finally began this week.

Workers began unloading 20-ton lengths of steel track in Lewisville and Lake Dallas along the route of the old Missouri-Kansas-Texas Railroad. The 1,600-foot lengths of steel will form the backbone for the new 21-mile railway that is expected to be completed by December 2010.

“This is the first evidence that real progress is taking place,” said Dee Leggett, a spokeswoman for the Denton County Transportation Authority, which is managing the project. “We’ve been talking about this for so long.”

The commuter line will stretch from Denton to Carrollton, where passengers can transfer to the Dallas Area Rapid Transit’s Green Line and travel to Dallas. The Denton-to-Dallas commute will take about 70 minutes.

Once the quarter-mile lengths of track are unloaded, workers will begin laying the rails in Denton and Carrollton.

“The goal is to meet in the middle over Lewisville Lake,” said Kimberly Durnan, public information manager for the North Texas Rail Group, which is constructing the $314 million transit project.

The A-train project is scheduled to be completed at the end of 2010 to coincide with the opening of the northern terminus of the Green Line in Carrollton.

While some have felt that Denton County isn’t ready for a commuter rail service, transportation authority officials believe that the A-train will draw 4,000 to 5,000 passengers a day when it opens, Leggett said.

And she expects those numbers to grow with Denton County’s increasing population.

Cities along the line hope the A-train will be an engine for economic development.

Lewisville will have three rail stations, including one east of its historic Old Town area where officials have just broken ground on a $10 million arts center. Denton will have two stations.

Two new apartment projects are in the works in downtown Carrollton, which expects to be the hub for three rail lines, and DART’s Trinity Mills transfer station will support A-train railway passengers.

Unlike DART’s light-rail transit system, the A-train will be commuter rail, with stations spaced farther apart and passengers traveling aboard diesel-powered vehicles instead of electric train cars.

The new tracks will be welded together to provide a smoother, quieter ride for commuters and less noise for residents who live along the train’s path, Durnan said. And, she added, “quiet zones” will be established along the entire A-train corridor.

“The No. 1 concern has always been noise,” Durnan said.