Expect road closures in Grapevine this weekend as interchange project reaches ‘milestone’ The $371-million I-635/SH 121 Interchange project aims to increase connectivity among major highways in the area but will cause road closures this weekend. Expect traffic and closures along State Highway 121 through the weekend.(Kye R. Lee / Staff Photographer) Expect congested roads this weekend along State Highway 121 through Grapevine, as the $371-million Interstate 635/SH 121 interchange project hits a major milestone. According to the city, traffic will shift this weekend to the new southbound SH 121 main lanes as the southbound part of the highway enters its final configuration, with an increased number of lanes.