The Challenge Miami Triathlon will be closing Card Sound Road traffic from 7:30 a.m. to 1 p.m. on Sunday, March 14. Motorists will take the 18-Mile Stretch as a detour during those times, according to Monroe County Sheriffâs Office spokesman Adam Linhardt. Racers will leave the Homestead-Miami Speedway and eventually head south on Card Sound Road to Alabama Jacks and turn around, heading back to the race track, Linhardt said.