Train horns must be sounded in a standardized pattern of 2 long, 1 short, and 1 long blasts. The pattern must be repeated or prolonged until the lead locomotive or lead cab car occupies the grade crossing. The rule does not stipulate the durations of long and short blasts.

Yes, in 2026, North American railroads still strictly follow a standardized set of horn signals (whistle codes) established by the General Code of Operating Rules (GCOR) to communicate with track workers and the public. These codes consist of combinations of "Long" (—) and "Short" (o) blasts. The most common signal is — — o — (two longs, one short, one long), which must be sounded at every public highway grade crossing. Another vital signal is o o o, used when a train is backing up. A succession of short blasts serves as an urgent warning for people or livestock on the tracks. Conversely, two short blasts (o o) are a standard acknowledgment of a signal given by another employee. While modern digital radio communication has replaced many historical whistle codes, these audible horn patterns remain a mandatory safety requirement to ensure that anyone near the tracks—even those without a radio—understands the locomotive's immediate intentions and movements to prevent accidents.