This proposed highway reconstruction project is for a 17.4-kilometer (10.8-mile) section of U.S. Highway 212/310 between Carbon and Yellowstone counties in south-central Montana, along with a short section of U.S. Highway 310 southwest of Rockvale. The alternative preferred by MDT and the Federal Highway Administration would involve "shifting" the alignment west-northwesterly with grading, paving, new structures, guard rails, and fencing, and would include access to both the present route and adjacent or nearby properties. That Preferred Alternative, designated Alternative 5B--Combined West Bench herein, would be a four-lane divided facility between the Rockvale area and the existing four-lane highway southerly of Laurel. Principal environmental impacts would be to land use (primarily in farmlands), traffic noise, water resources (an intermittent stream and irrigation ditch crossings), and wetlands. Some residential relocations are expected.