In the wake of a series of deadly spills, the safety of crude oil traveling on railroads has become a national question. A new federal rule requiring railroad companies to notify state officials where Bakken oil is moving went into effect last week (although railroad companies are doing all they can to keep routes secret). Yet the most basic questions about crude-by-rail – how much oil is moving on railroads and where exactly is it going – have proven difficult to answer. How much crude oil is moving on U.S. railroads? It depends on who you ask and how you ask.