Here’s why you hear that train a-comin’ in downtown Cedar Rapids

The Train Horn Rule is administered by the U.S. Department of Transportation's Federal Railroad Administration.

Under that rule, locomotive engineers must begin sounding a train whistle at least 15 seconds - and no more than 20 seconds - before they reach all public grade crossings. There are variations to that rule based on the train's speed or when engineers can't precisely estimate the arrival at a crossing.

Train horns are sounded in a pattern of two long, one short and one long blasts. The rule does not specify the duration of a long blast compared with a short blast, but the pattern must be repeated or prolonged until the lead cab car reaches the crossing.

Locomotive horns are required to reach a minimum of 96 and a maximum of 110 decibels.

The rule also allows municipalities the option of reducing train horn frequency by establishing quiet zones.

In those zones, railroads have been directed to cease the standard use of horns when approaching an approved crossing. Engineers still have discretion on horn use in quiet zones, such as during emergencies.

To receive Federal Railroad Administration approval for a quiet zone, municipalities first must mitigate the increased risk caused by the absence of a horn.

A quiet zone must have at least flashing lights and gates at the railroad crossing.