On April 27, 2005, the Federal Railroad Administration (FRA), which enforces rail safety regulations, published the final rule on the use of locomotive horns at highway - rail grade crossings. Effective June 24, 2005, the rule requires that locomotive horns be sounded at all public grade crossings at least 15 seconds, but not more than 20 seconds before entering a crossing. This rule applies when the train speed is below 45 mph (70 km / h). At 45 mph or above, trains are still required to sound their horn at the designated location (usually denoted with a whistle post).
when do trains have to blow their horns
at all public grade crossings