My after-work, solo, rides are on narrow roads with a few hills and curves. Generally I ride in the middle of my lane on the flat, straight portions and make a conspicuous move to the right when vehicular traffic is approaching from the rear. On the hills and curves, I hug the right side and stay on the road. If I can see that an approaching vehicle will make it impossible for a vehicle behind me to pass, I extend my hand out with my palm facing to the rear to indicate that it is not safe to pass. So far, the drivers have understood this signal. When it's clear ahead, I wave them around. This has worked as well. When I have a vehicle behind me on a hill or curve, I increase my speed to decrease the amount of time the vehicle has to wait on me. So far, so good.