alsorailfan wrote:Is size 4 what we normally see along the surface of the ballast? What size do they put down first? And what size do they use for the grade crossing?
First a correction on my part:
The stone being used is number 3 stone.
And onto your question.
Number 4 is larger stone and more common on high tonnage, high speed lines. Number 4 is also most effective for erosion control and maximum drainage. Number 3 works well for most railroads and is probably still the most common today. Number three can be used all throughout the railroad including Up to crossings, few public crossings, if any, are laid in stone. Asphalt is usually preferred. Number 3 stones are usually between 1 and 2.5 inches. Number four is usually 2 to 4 inches.
I'm no expert on this but I've been told that 3A can be used as sub-road as it packs pretty well.
The thing to remember is simply because number 3 three sotne was used when the track was installed or repaired or replaced, does not mean that years down the road, the stone will be in the same condition, it packs, it chips, it settles, it becomes contaminated (with soil, and other non ballast materials), amongst other things.
Again, I am no expert on the matter but this is what I have learned in conversations and by reading and a dash of experience here and there. YMMV.