Driveway Erosion Problem
One of the things I have done in the past with crushed rock driveways is pack it with a roller or plate compactor until there is no movement, then use some Portland cement on the surface and broom the surface so the cement gets in the cracks, this is not a big area but with a bus or other heavy equipment using it the cement (dry powder) swept in and a light sprinkle with water will help it hold. As an example my last home 1 of the driveways dropped 30’ in 70’ steep. It was crushed quarry. I used several bags of Portland cement it never washed out and really stayed in place quite well for many years.