Train horn

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Train horns are audible warning devices found on most diesel and electric locomotives. They most commonly are used for internal communication between train staff, i.e. during shunting operations, and for warning purposes to members of the public who are near on on the rail line, for example on a level crossing.

Contents 1 History and background 2 Operation 3 Train horns worldwide 3.1 North America 3.1.1 United States 3.2 Germany 3.3 France 4 Location and placement 5 Train horns and popular culture 6 See also 7 External links 8 References

[edit] History and background

As diesel locomotives began to replace steam on many railroads, it was realized that the new locomotives were unable to utilize the steam whistles then in use. Early internal-combustion locomotives were initially fitted with truck horns, but these were found to be unsuitable, and so the air horn design was modified for railroad use.

[edit] Operation

Classic train horns are operated by compressed air, typically 9-10 bar (130-145 psi), and fed from a locomotive main air reservoir. On American locomotives built prior to the early 1990s, they are actuated by a manual lever or pull-cord. Current American locomotives, as well as European models built since the mid-1960s, make use of pushbutton controls.

The basic operation of a train horn, or most any air horn for that matter, is that the air flow throughout the horn causes oscillation, producing sound waves. Oscillation in a train horn is accomplished via a diaphragm. When air is applied to the horn, the diaphragm begins to vibrate. Since the position of the diaphragm at any given moment during the vibration will allow more or less air through the horn, the constant oscillation of the diaphragm causes "waves" of air which in turn produce audible sound.

The configuration and dimensions of the bell ("bell" being the correct term for the trumpet assembly) determine the frequency produced (measured in Hz), and hence, the fundamental.

Many early three and five-note train horns were designed to play basic musical chords.

[edit] Train horns worldwide

The meaning of horn signals varies from country to country. Most countries with large former or current state-owned railway networks, like France, Germany or Great Britain, use standardized meanings of horn signals on their networks, whilst in other countries, for example the United States, meanings of horn signals can vary between railway operators.

[edit] North America

Main article: Train horns in North America

There have been six major manufacturers of air horns for railroad use in North America. Of these, only Airchime, Ltd. and Leslie Controls, Inc. remain today.

[edit] United States

Railroads are required by a variety of state and federal laws to sound horns in advance of all crossings. Horns are sounded to warn of approaching trains.

On April 27, 2005, the Federal Railroad Administration (FRA) published the final rule on the use of locomotive horns at highway-rail grade crossings. The rule requires that locomotive horns be sounded at all public grade crossings 15-20 seconds before entering a crossing, but not more than one-quarter mile (400 m) in advance. This rule applies when the train speed is below 45 mph (70 km/h). At 45 mph or above, trains are still required to sound their horn at the designated location (usually marked with a whistle post).

The following are the required horn signals listed in the operating rules of most railroads, along with their meanings. Signals are illustrated by a "." for short sounds, and "-" for longer sounds.

Rule number	Sequence	Meaning
14 (a)	.	Apply air brakes.
14 (b)	- -	*1. Proceed, 2. Release air brakes.
14 (g)	. .	Generic acknowledgement.
14 (h)	. . .	*Back up.
14 (j)	. . . .	Calling for signals.
14 (l)	- - . -	1. Approaching public crossings at grade. The signal will be sounded until the train is on the crossing 2. Approaching tunnels, yards, or other points. 3. Passing standing trains.
14 (o)	. -	Inspect train for a leak in brake pipe system or for brakes sticking.
14 (p)	Succession of sounds	Warning to people and/or animals.
14 (q)	- .	When running against the current of traffic: 1. Approaching stations, curves, or other points where view may be obscured: and 2. Approaching passenger or freight trains and when passing freight trains.

[edit] Germany

Horn signals are regulated in the Zp category of the Eisenbahn-Bau- und Betriebsordnung. Their most common use today is when approaching a level crossing that lacks barriers, and for warning purposes.

Whistle posts are labelled with the letter "P" (for 'Pfeifen'). Common signals are:^[1]

Sequence	Meaning
-	Zp 1 - Generic "Attention" signal.
.	Zp 2 - Tighten handbrakes.
. .	Zp 3 - Strongly tighten handbrakes.
- -	Zp 4 - Loosen handbrakes
... ... ...	Zp 5 - Emergency. Brake immediately.
- . -	Zp 11 - Come. Used to call out for train staff.

[edit] France

Train horns are sounded where a whistle post (marked with the letter 'S' for 'siffler') is present. If the whistle post is labelled 'J' (meaning 'jour'), the horn is only to be sounded between 07:00 and 20:00. Horns must also be sounded when passing an oncoming train, shortly before reaching the last car of the train.

[edit] Location and placement

As many people do with their personal vehicles, railroads order locomotives with many different options in order to suit their operating and maintenance practices.

Horns are no exception, and railroad mechanical forces mount these on locomotives where they are deemed most effective at projecting sound. Below are a few images depicting the most common mounting locations:

On many locomotives with high short hoods, such as this Norfolk Southern GP38-2, the air horn can be located away from the operating cab.

AirChime model K5H mounted on a custom bracket. Not only is the horn located here, but the air-operated bell as well.

On newer locomotives, the horn is mounted atop the engine compartment due to complaints from train crews. However, acoustic performance suffers, and the sound is often muffled.

European locomotives often have their horns in less prominent locations than their American counterparts. This DB Class 155 engine has the horn simply placed below the cab windows.

[edit] Train horns and popular culture

Fitting a train horn to trucks or an SUV has become the current fad of many vehicle customizers.^{[citation needed]} Recent years have seen an increase of horn theft from railroad property, it is believed that the great majority of these crimes are perpetuated for the benefit of vehicle customizers and truckers.^{[citation needed]}

On the other hand, there are those who collect train horns for their rarity and nostalgic value. Such items can command high prices among collectors.

Due to the encroachment of development, some suburban dwellers have opposed the railroad use of the air horn as a trackside warning device. This despite the fact that in most locations, the railroad had been established long before the development sprang up.

Residents in some communities have attempted to establish quiet zones, in which train crews are instructed not to sound their horns, except in case of emergency. Given the speed at which many trains travel, as well as the disparity in mass between railroad equipment and an automobile or truck, incidents often occur without warning. The effects of a train colliding with an errant automobile have been likened to that same automobile striking an empty soda can.^{[citation needed]}

A ban on sounding locomotive horns in Florida was ordered removed by the FRA after it was shown that the accident rate doubled during the ban. The new ruling preempts any state or local laws regarding the use of the train horn at public crossings. This also provides public authorities the option to maintain and/or establish quiet zones provided certain supplemental or alternative safety measures are in place, "and the crossing accident rate meets government standards".

[edit] See also

• Train whistle

[edit] External links

• Five Chime Consultants - The original online spotters' guide to diesel locomotive horns as used throughout the United States and Canada. Fully illustrated, with audio samples and background information on each horn.

• Leslie Controls, Inc. - Makers of SuperTyfon brand air horns for rail, marine, and industrial use.

• Nathan Airchime Manufacturing - Original designer of train horns heard throughout the world.

[edit] References