OMAHA, Neb. (AP) — The fiery derailment of a train carrying toxic chemicals when it went off the tracks — sending a huge plume of smoke in the air and forcing residents of a small Ohio town to evacuate — has highlighted the potentially disastrous consequences of train accidents and raised questions about railroad safety. The railroad industry is generally regarded as the safest option for most goods and federal data show accidents involving hazardous materials are exceedingly rare.