The planned bridge east of University Drive and south of West Lancaster Avenue is estimated to cost $10 million to $12 million. It's part of the Southwest Parkway toll road, a complicated project that involves the railroads, Fort Worth, Texas, Department of Transportation and North Texas Tollway Authority.

Although T officials aren't expecting to open commuter rail service in that area until 2012 or 2013 at the earliest, they decided that it would be more cost-effective to contribute to the project now rather than wait a few years.

The T's portion of the bridge will be paid for from the agency's rail reserve fund, a savings account of sorts for the commuter rail project.

The proposed rail line would run from southwest Fort Worth to Grapevine.

The T board approved the payment Oct. 15. Southwest Parkway is scheduled to be under construction next year.