The southbound I-35 Frontage Road and 51st Street intersection will close temporarily this weekend, as the Texas Department of Transportation prepares to open the first phase of the new roundabout. The southbound I-35 Frontage Road will close at 9 p.m. Thursday, Feb 8, and traffic will be detoured to the intersection bypass lane. Eastbound 51st Street will be closed at the southbound I-35 Frontage Road, and westbound 51st Street will be reduced to one lane. At 10 a.m. Friday, Feb. 9, the southbound I-35 Frontage Road will close to drivers headed west on 51st Street. They will be detoured through the intersection to Airport Boulevard. At 5 a.m. on Sunday, Feb. 11, one lane will open in the roundabout. Traffic signals will be removed, and officers will be on site to direct traffic through the new intersection. The roundabout, which is expected to be completed by spring, will ultimately include two lanes. The $16.5 million project is being constructed by Capital Excavation Company.