Railroads in Minnesota are working toward full implementation of technology that could help prevent rail accidents. Positive train control uses GPS technology to determine a train's location and can override the operator if necessary. It's a complex system that still has yet to receive federal certification. There is growing concern in the industry that the current 2015 deadline is unrealistic given the complexity of the technology. "This has never been done before," said Association of American Railroads spokeswoman Holly Arthur.