If the current and future gravel is crushed and not rounded, then I would think the 4 inches would be adequate. If the stones are rounded, then no depth is adequate. I have crushed stone drive. The stones are pea gravel sized but they are faceted and not round. Once they are locked into place, they don't move around. Mine does not have a border, either.

I agree, mowing and whackin and flying stones stink. What weeds or grass are you having to wack? You need to know what so you know how to get rid of them first. Depends on what's there as to how to get them gone. Is your old driveway in sun or shade? There are lots of plants that don't need wackin that would love to grow Zone 6 gravel. Tell more about your driveway area and someone will help. Annie

joepyeweed's list is good, but you'll need a fair amount of seed for a 150' drive. Flowering spurge seed is very expensive, and butterflyweed and prairie smoke can be expensive as well. Coreopsis would be a good choice, but will not persist. It is a short-lived perennial. Black-eyed susan would be another good choice, but is likewise short-lived. Wild lupine (Lupinus perennis) would be another good choice. Spiderwort and prairie drop seed are great plants and seed is pretty inexpensive. Another good plant to consider would be rough blazing star (Liatris aspera).

dftush, That does sound heartbreaking. As a general rule, be assertive in looking out for your own interests when it comes to dealing with your neighbor or anyone else. Also, explain the reason WHY you do or don't want contractors, neighbors, and others to do things or not do things a certain way. It's possible your neighbor thought you felt guilty about him plowing because you weren't paying him and had no idea you were proud of your driveway and that the plowing would cause significant damage. Of course it's also possible that he's just one of those people who "doesn't get it" because his brain is wired a different way and he doesn't have a sense about when he is causing damage, and will do things even when told not to. Get an estimate for the repair of your driveway and ask your neighbor to pay for it. Don't accept any offers for him to fix it himself. (Basically he can't be trusted to do it properly, no matter how much of a nice guy he may be.) If he will not pay, ask the company whose truck he drove to pay for it. The company may not have to pay out of pocket if they have insurance for damage caused by plowing. If they will not, gather your evidence (it will be helpful if you took before and after photos) and take both your neighbor and the company that owns the truck to small claims court. For use in dealing with the police or court system in the future, write him letter and send it certified mail informing him you do not want him to plow your driveway and if he does, you will consider it trespassing and report it to the police. Mail a copy to the company that owns the truck as well. Keep the a record of sending the letter, including the delivery confirmation receipts for your records. If he STILL doesn't take the hint, you might consider putting a locked gate at the end of your driveway, or parking a car across the end of the driveway when it snows.