Trains usually honk loud during night time in order to keep away deadly creatures such as cows, and other wild animals that may be prowling on the track on which the train is approaching. Cows are the most difficult animals next to elephants due to their tough horns and tusks of the elephant.

Contrary to popular belief, trains do not "only" honk at night; they are actually required by federal law (in the U.S., the FRA "Train Horn Rule") to sound their horns at all public grade crossings, 24 hours a day. The reason it seems like they only honk at night is due to acoustics and psychology. At night, ambient city noise—traffic, construction, and general "hum"—dies down significantly, allowing the 96–110 decibel blast of a train horn to travel much further and sound much louder against the silence. Furthermore, people are usually home and trying to sleep, making them much more sensitive to the sound than they would be during a busy afternoon. The specific pattern required is two long, one short, and one long blast, which must begin 15–20 seconds before the train reaches the crossing. While some cities have established "Quiet Zones"—where trains don't honk unless there is an emergency—these require expensive safety upgrades like additional gates and medians. In most of the country, the "nighttime honking" is simply the sound of safety regulations being followed to prevent collisions in low-visibility conditions.