Alongside the Skyway route in Chicago, there is an interlocking by a Norfolk Southern intermodal yard. The north end of the plant is guarded by a “Lines West” style bridge and the south end by a “Lines East” one. At Western Avenue Tower A-2, there are two extended length “Lines East” bridges over the ex-Milwaukee Road and our tracks (UP/ex-CNW). Just past the former location of Noble Street Tower is a “Lines West” bridge over Metra’s tracks. My question: why the differences and what determined what got built where?