<P> 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). </P> <P> The pattern for blowing the horn remains two long, one short, and one long . This is to be repeated or prolonged as necessary until the lead locomotive fully occupies the crossing . Locomotive engineers retain the authority to vary this pattern as necessary for crossings in close proximity, and are allowed to sound the horn in emergency situations no matter where the location . </P> <P> A ban on sounding locomotive horns in Florida was ordered removed by the FRA after it was shown that the accident rate doubled during the ban . The new ruling preempts any state or local laws regarding the use of the train horn at public crossings . This also provides public authorities the option to maintain and / or establish quiet zones provided certain supplemental or alternative safety measures are in place, and the crossing accident rate meets government standards . </P> <P> The following are the required horn signals listed in the operating rules of most North American railroads, along with their meanings . Signals are illustrated by an "o" for short sounds, and "--" for longer sounds . (Note that these signals and their indications are updated to reflect modern practice .) Those rules marked with an asterisk (*) must be sounded when and / or where applicable . Those signals without an asterisk convey information to employees; they must be used when voice communication is not available . </P>

When does a train have to blow its horn