CARMEL, Ind. -- Carmel residents who came out Thursday to review plans to upgrade U.S. 31 saw a familiar concept in INDOT's proposal: roundabouts.

The Indiana Department of Transportation is proposing two roundabouts along U.S. 31 in Carmel: one at 136th Street and the other at 131st Street, 6News' Norman Cox reported.

If approved, the roundabouts would be the first of their kind on any U.S. highway.

However, officials said, the proposal is still in the early stages.

"We haven't made too many decisions yet as we get closer to this project. So really, it's a good time for people, if they have an opinion, to get it expressed, get it included in the official record, so that we can take those comments into consideration when we go into the design of this project," INDOT Spokesman Will Wingfield said.

The nearly $500,000 project, paid for with money from the state's Major Moves fund, will remake the transportation system of Hamilton County.

INDOT will upgrade U.S. 31 from Interstate 465 on the south, to 216th Street on the north, adding 11 interchanges to make the highway interstate-quality.

Work will tentatively begin in 2011, when Carmel is expected to be finished upgrading Keystone Avenue. Construction is estimated to take seven years.