A River Rail extension to Little Rock's airport is moving forward as local governments look for a consultant to map out a route and determine a cost for branching out from downtown.

Three transportation consulting firms in the last week answered requests for proposals from Metroplan, central Arkansas' regional planning agency, for a feasibility study about linking streetcar tracks in Little Rock's and North Little Rock's downtowns with Little Rock National Airport, Adams Field.

The airport's terminal is about three miles from the streetcar's easternmost stop near the Clinton Presidential Library and Heifer International.

"It's really as much of a route study as it is a feasibility study," Pulaski County Judge Buddy Villines said Friday. "There was a study in the late 1980s that said going from downtown to the airport was feasible back then. If we could lay out where the route is going it would give us an idea of what the cost will be." The study would consider alternative routes, the use of new track or existing freight rail track, and costs. Results could be complete in six months, Villines said.

Metroplan advertised for proposals on behalf of the county, Little Rock and North Little Rock. Metroplan will form a committee to choose the best proposal then negotiate the consultant's price within about a month, said Jim McKenzie, Metroplan's executive director.

The companies are: Carter & Burgess Inc. of Fort Worth; URS Corporation of Fort Worth; and Wilbur Smith Associates of Columbia, S.C. Carter & Burgess has a branch office in Little Rock.