Update 2:58pm: All southbound lanes are closed. Traffic gets by on the shoulder. A traffic incident has closed two lanes of I-270 in Gaithersburg on Thursday, February 15. The Montgomery County Office of Emergency Managament and Homeland Security tweeted the following at 12:57pm: “Traffic incident closes two left lanes of southbound I-270 before Watkins Mill Road (Exit 12). Expect significant delays. Seek alternate route. #MdTraffic”