In Ames, Iowa, an automated horn warning system that alerted motorists and pedestrians of oncoming trains reduced the area impacted by noise levels greater than 80 dBA from 171 acres to less than 6 acres.
Date Posted

Evaluation of an Automated Horn Warning System at Three Highway-Railroad Grade Crossings in Ames, Iowa

Summary Information

This report summarizes the impacts of the installation of an automated horn system to warn motorists and pedestrians at three highway-rail grade crossings in Ames, Iowa (population 48,000). Flashing lights and gate arms existed at the intersections to warn motorists of an oncoming train, however locomotive engineers were required to sound the train’s horn to provide an audible warning at the crossing. Approximately 60 trains cross the intersections during a typical 24-hour period, which lead to noise complaints from nearby residents.

The new system, installed in September 1998, eliminates this need by sounding to two smaller horns located at the roadside and aligned in the direction of the roadway approaches to the grade crossing. Track signal circuitry, which also triggers the lights and gate arms, activates the roadside horns and a strobe light along the railroad which notifies the locomotive engineers that the automated system in operating. Engineers only need to sound their horns if the system is inoperable, or if they feel that a dangerous situation exists at the crossing.

The evaluation described in this report examined the changes in noise levels in the area before and after installation of the automated horn system, and the opinions of residents, motorists, and locomotive engineers regarding the system. Horn volume readings, in decibels (dBA) were taken in a grid pattern surrounding the intersections.


Results indicate that the area impacted by a noise level greater than 80 dBA decreased by 97 percent with the implementation of the automated system, from 171 acres to less than 6 acres. For comparison, the volume of a person shouting from 3 feet away is approximately 78 dBA.
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