USA Horn Signal at Crossing Question

I know that the FRA requires engineers to sound the horn in a long-long-short-long pattern when approaching a crossing, but I've noticed sometimes that two short blasts will be made after the long-long-short-long pattern. Anyone know why?

I know, according to the timetable I have, that between some mileposts its required to do 2 short blasts 100 feet before a grade crossing.

Every engineer has his own style of blowin' the whistle/horn. Take this video for example: http://m.youtube.com/#/watch?v=HQvIW4eIoaI

The key word is "requires". The FRA is looking to give the railroads a bare standard to what needs to be done at a crossing, something that gives a solid indication of the presence of a train to the public and road workers. This does not forbid the engineer from exercising caution beyond the pattern adding additional blows to the sequence. What it comes down to is the engineer's judgement of the safety of the situation, this is an alerting system after all. If the situation seems hazardous, it may warrant further horn sounds to ensure public and road worker safety (areas such as tight curves, places of heavy view obstruction, or heavy crowd presence). Comes down to common sense and safety really.

It could also be timing. If the engineer blows a bit late, he will short-horn blow after crossing the road.

John

Also he is required to blow up until he reaches the crossing, so if the blows the usual pattern a bit early he may need to add a few more toots to reach the crossing.