PHILADELPHIA (AP) — Sarah Feinberg was on the job as the nation's chief railroad regulator for just three weeks when a packed commuter train slammed into an SUV stopped on tracks north of New York City, killing six people. During Feinberg's tenure, the Federal Railroad Administration has aggressively policed safety violations, closing cases at a higher rate and collecting more fine money per year than her predecessors. As oil trains continued to derail and catch fire, Feinberg again turned to technology, championing modern electronic braking systems. [...] with a link between recent commuter train crashes and sleep apnea becoming clearer, Feinberg issued a safety advisory urging railroads to test engineers for the dangerous, fatigue-inducing disorder. Technology companies have started adding railway crossing locations to GPS devices and mapping applications, warning motorists as they approach. At her confirmation hearing, Trump's Transportation Secretary nominee, Elaine Chao, was non-committal on the deadline for installing speed controls saying she needed a briefing on the technology before answering.