Decreasing Emergency Railroad Accident Instances Locally Act or the DERAIL ActThis bill requires the Department of Transportation (DOT) to expand the definition of a high-hazard flammable train (HHFT), thereby subjecting more trains to additional safety requirements.Specifically, DOT must expand the definition of HHFT to mean a train transporting one or more loaded tank cars of a Class 3 flammable liquid (e.g., benzene residue) or a Class 2 flammable gas (e.g., vinyl chloride) and other materials DOT determines necessary for safety. Current regulations define HHFT as a train transporting 20 or more loaded tank cars of a Class 3 flammable liquid in a continuous block or 35 or more loaded tank cars of a Class 3 flammable liquid dispersed throughout the train.The bill also requires railway carriers to report a train derailment that involves a train carrying material toxic by inhalation within 24 hours of the derailment to the National Response Center (NRC), state and local officials, and tribal governments. As background, the NRC is a part of the federally established National Response System. Reports to the NRC activate&nbsp;the National Oil and Hazardous Substances Pollution Contingency Plan and the federal government's response capabilities.