Why is "long long short long" always blown by trains at RR crossings?

Question

Why is this sequence "long long short long" always blown by an oncoming train at railroad crossings? All I can find is that it means "Q" in american morse code.

Answer 1

Its a railroad regulation in a book called the GCOR general code of operating practices and a requirement with the FRA federal railroad administration.

Answer 2

Hoghead: CQD is "Seek You - Distress"

CQ is the general message used in Morse code by radio amateurs ("Hams") who wish to talk to another user.

"SOS" has an easily remembered dot-dash sequence which was one of the reasons for the change.

Answer 3

To echo Derail's comments I believe the sequence simply evolved into becoming the standard whistle/horn sequence that must be used (for safety reasons) at every crossing to alert motorists and anything/anyone potentially blocking the right-of-way to move off the tracks and stay away until the train has completely passed.

Answer 4

How to whistle a crossing in Canada, is written in the Canadian Rail Operating Rules (CROR).

It is also , long, long, short, long. Starting 1/4 mile from the crossing and finishing the last long blast when the crossing is fully occupied.

Answer 5

I don't know how the sequence became convention, but I can tell you why they use it. Long-long-short-long ensures that the horn will be sounded at a sufficient distance from the crossing, alerting those in the area of the approaching train. If we were only required to sound one long blast, we would already be right there at the crossing!

Answer 6

Excellent question.

Of course I can't speak to all of rail history, but your question got me to looking at some of the railroad artifacts in my collection.

I would agree with the above, that at some point in time, this signal became the standard.  It should also be noted that, in addition to rule requirement, it is the law in every State of the Union that this signal be sounded when approaching rail crossings at grade.

But, where did it come from?  I would suspect from an Eastern railroad, those having been in existence for at least three decades before the rails reached the west coast.  So, I have looked backwards at my Southern Pacific stuff.  

I can't say when this signal was adopted, for sure, but I can say this:

Ref:  Southern Pacific Company, Pacific System, Oregon and Woodland Divisions, Time Table No. 7., To Take Effect Sunday, November 1, 1891, at 10:00 A. M.

Rule number 6:

One sound of the whistle is the signal to apply the brakes.

Two sounds of the whistle is the signal to let go the brakes.

Three sounds of the whistle is the signal to back.

Four sounds of the whistle is the signal to call in a Flagman.

Five sounds of the whistle is a warning to men on top of freight cars that train is approaching tunnel or covered bridge.

One long and two short sounds of the whistle in quick succession is the signal when approaching road crossing.

Two long, followed by two short sounds of the whistle in quick succession is the signal to be given by trains when displaying signals for a following train, to call attention of trains of the same or inferior class to signals displayed.

So, at least out west, and sometime after 1891, the two longs, short and long so familiar today was adopted.  

You've got me curious now, and I'll look at some other stuff.  If I can narrow the window I will.

Addendum:  Something I forgot.  You mentioned the morse code "Q".  Prior to the sinking of the Titanic, in 1912, the symbol for distress in morse code was CQD.  The Titanic was the first to use the new code, SOS.

I would want to know what the "Q" in CQD stands for.  Perhaps that is tied in some way, hence the morse signal for Q adopted for crossings.

Answer 7

That's a good question. In many very old engineer rule books going back 100 years and more, this sequence designates "Approaching a Station".  I think it just evolved in to a common signal for all road crossings. I'm an engineer, and I know that is the required by current rule books for crossings. Hopefully, someone will add more to this.