Since you work for PennDot, check and see what they use for berm gravel (common term). It should be crushed limestone consisting of 67's (3/4") limestone, down to dust. Also known as 67D, and probably several other names. I'm retired from ODOT, so I know numbers can vary from different quarry's, and gravel pits. If you run cars, trucks & equipment across it, if put down pretty damp 2"-3" deep, it should pack well, and lock together. If it's in a circle drive, you may get a few stones to kick out. If straight, not so bad. But, it is best to have it wet, then roll several times with your tractor, and it will pack well.
With that being said, there are two types of limestone fresh water, and salt water. The fresh water stone is found closer to the surface, is softer, and will break down sooner, and basically turn to mud, under heavy traffic. Salt water stone is more preferred. It probably won't make that much difference in a driveway though.
If you have problems with a muddy paddock, #10, or, screenings limestone works great to keep a hard surface in there. I put it down approx. 4" thick, and rolled it in with my Bobcat. Again, this was put down wet. With the horses walking on it, compacts it even more. Some slope to shed water is even better. When it dries, it gets very hard. I clean the paddock with my Bobcat, and it's nearly like loading off concrete. I put the first down in 2012, and just now needing to top dress it.
In all of my French type drains here, I used #8 washed gravel, or, pea gravel. 99% of the drains we put in, when doing slip repairs on highways, this is what is used. For no more than it costs, I also put a 4" perforated pipe in, to keep it from silting in. The main concern is putting something on top of the gravel to keep dirt from sifting down through, plugging the drain. On the job, we used Geo-Tech cut in strips, and laid overt the gravel. It was left over from contractor jobs. They made it a policy to recoup materials left over from construction jobs. It came in handy for many jobs we did. Here at home, I use the better grade landscaping material. I've been called out on that one, but back years ago, when they put in leach beds around here, they covered the gravel with approx. 1' of straw for a dirt barrier. When dirt is put back, and finally settles, it won't be much over an inch thick mat. Same was done on the first few drains we put in years ago. We've had to go back and repair a few drains that were put in 10-15 years before I even started, and the straw was still there, although somewhat deteriorated, but still doing its job. As long as the air doesn't get to it, it will last for years. I put my drains in nearly 10 years ago, and all are still working like they should. All but one are covered with 6" to 8" of dirt, and sodded over. One in particular is in the one pasture. Water will pond in it after heavy rains, but will perk down through the sod and dirt within an hour. The one with gravel to the top, between buildings, I put the cloth down approx.6' to 8", then topped with gravel. It never ponds water, and has been in for 6 years or so.
