Mayor Ed Lee is floating the idea of tearing down the stub end of Interstate 280 in San Francisco in hopes of creating a new neighborhood and speeding up the arrival of high-speed rail service downtown. The idea, laid out by the mayor's chief transit planner, Gillian Gillett, in a memo to the regional Metropolitan Transportation Commission, would be to knock down I-280 before 16th Street - eliminating the ramps both at Sixth and Brannan streets and at Fourth and King streets. It would be replaced by a street-level boulevard akin to those built after the Embarcadero and Central freeways...