The South City Switcher has just dropped two boxcars of produce at a local warehouse. Now, headed back it must contend with the busy thoroughfare of 3rd St. The engineer brought the power up to the intersection and paused, while the signals started flashing red. Then he brought traffic to a halt with a long blast of a good old SP 3-chime and proceeded across. Note the people on the street corner plugging their ears. Note also the diamond with the MUNI Metro tracks - one of the few places in the country where light rail and heavy rail intersect.