 One disturbing part of the report shows South Dakota's exports declined by more than 11% from a year ago. The screams of motors pushing cars and motorcycles to dizzying speeds can be heard deep into the night in Sioux Falls nearly every summer night. And it's not just a few here and there. Street racing has become a craze attracting hundreds of fans. Night traffic officer Mark Tolan says they've developed new tactics to keep the races rolling.