Going down this hill on the way back from Box Hill and just when I saw the cars coming the other way there was a load of gravel in the road. Whilst braking wheels repeatedly locked up and I nearly came off the bike in the path of the oncoming traffic. I think it's only luck that I didn't get hit by either vehicle. I was already being cautious on the way down as I've seen nasty accidents before. I was not pedalling and was on the brakes. Any advice about what else I should have been doing?