On Monday, the Chicago Transportation Authority announced plans to close the southern leg of the Red Line for five months in 2013. For Tuesday's Eight Forty-Eight, WBEZ history blogger John Schmidt recalls past transit interruptions and quizzes listeners on the history of the 'L.' And NPR correspondent Julie Rovner covers the constitutionality of President Obama’s Affordable Care Act, which the Supreme Courtis slated to rule on later this month. To join the conversation, call 312.923.9239. Plus, Chicago duo Poor Elvis plays their rollicking rockabilly throughout the show.