Sound Advice
Volume 12, Issue 3, Fall 2009  

Wayside Horn System Test

Federal Law currently mandates that all trains sound their horns before entering any public grade crossing. For trains traveling at 45 mph or less, a combination of long and short horn blasts is generally required for 15 to 20 seconds before the crossing. For trains traveling faster than 45 mph the horn blasts are required within one quarter-mile of the crossing. The maximum noise level is required to be between 96 and 110 dBA at a distance of 100 feet. Clearly, for residents living near to railroad crossings, this represents a significant noise source. A local municipality (and existing Wieland Acoustics client) is currently investigating possible ways to reduce train-related noise impacts on its residents. Our firm was recently invited to observe their testing of a possible alternative to the traditional train horn – a Wayside Horn System.

A wayside horn system consists of a set of loudspeakers that are permanently installed at a railroad crossing. Any oncoming train automatically triggers the loudspeakers to broadcast the pre-recorded sound of a train horn as a warning to nearby motorists and/or pedestrians. Federal Regulations require that wayside horns must provide a maximum sound level of between 92 dBA and 110 dBA when measured 100 feet from the centerline of the nearest track (a slight reduction compared to the required range for train-mounted horns levels). With the wayside horn system in place, the oncoming train is no longer required to sound its onboard horn.

The test system demonstrated a number of features that could help to minimize horn noise levels:
 
1) The duration and level of the horn sound can be accurately controlled. Noise surveys conducted previously by Wieland Acoustics indicate that there is a wide variation in the actual noise levels generated by onboard train horns. The variation is partly due to differences in the horns themselves and partly due to how they are operated by the train drivers. Nearby residents report being more annoyed when they perceive that train drivers are “laying-on” their horns more than is strictly necessary. Because the wayside horn system is electronic it can be set to the minimum required sound level almost as easily as you can adjust the volume on your car stereo. This level will then be consistent for each train that triggers the system.

2) The wayside horn loudspeakers have high directivity; this means that most of the sound output is projected in whichever direction the loudspeaker is facing. With the loudspeaker mounted on a high pole this allows noise to be directed downward toward people and/or vehicles close to the crossing, reducing the amount of horn noise projected into the surrounding community.

3) The horn noise is localized to the actual crossing where the safety warning is most important, rather being generated along a quarter-mile stretch of track. This serves to reduce the “acoustical footprint” of the horn noise.

With the advantages listed above, the achievable noise reduction is ultimately limited by the minimum sound level requirement of 92 dBA at 100 feet. Lower noise levels may be permitted if the wayside horn system is installed in a designated “Quiet Zone” or if a waiver is obtained from the relevant authorities. In these cases the permitted level will be dependent on the specifics of each crossing. Having witnessed the system in use at sound levels both above and below the 92 dBA threshold, it is clear that in appropriate locations, levels below 92 dBA should be more than adequate for making it clear that a train is coming. However, the impact of a lower noise level from a static source would be less dramatic than that of a higher level sound coming from a train charging toward you.

It will be interesting to follow the progress of future wayside horn installations and see what, if any, reductions in the required noise levels are permitted. Typically, there may be pressure from the community to operate these systems as quietly as possible, but this will need to be balanced by the need to maintain noise levels that are loud enough for their intended purpose. When it comes to avoiding railroad accidents, a little noise can go a long way!

Related Article 1: In the November 5th, 2009 issue of Tustin News, a free Orange County Register publication, a front-page story was published entitled "Quiet Zone Ahead: Residents Want Trains to Lay off the Horn."  The article described plans by Tustin's City council to upgrade the intersection at Red Hill and Edinger Avenues with a median, additional gate arms, a pedestrian gate and a pedestrian bridge in support of its application for Quiet Zone status, which will eliminate the sounding of train horns except in an emergency. Residents are looking forward to the establishment of the Quiet Zone and an end to the sound of the horns.

The Tustin News article included some interesting statistics provided by Orange County Transportation Agency:
Nine Orange county cities have railroad crossings
45% of motorists accelerate as railroad barrier arms descend
64% of people ignore train warning signs, and
80% of the public are not aware of basic railroad crossing rules.

With stats like that it seems wise to install four quadrant gates and a pedestrian gate at each railroad crossing to increase safety even if the local municipality is not applying for Quiet Zone status.

Related Article 2: For an earlier related article from Wieland Acoustics, entitled "Train Horn Sounding", click here.

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