Here are a couple of dilemmas about considerate driving.
I arrive at a busy main road on a side road, a kind driver lets me in, and I wave to thank him. Fifty yards down the road, there's another side road with somebody waiting to get in. Do I give way, thereby emulating the courtesy of the driver behind me, but giving him a small reason to regret his generosity, or do I push on, because I owe it to the driver behind not to hold him up any more? I usually give way, but I can see that if this happens enough, the public spirited driver may never reach his destination.
The road I'm driving down has a short single-lane pinch point because of cars parked on both sides. There's no obvious priority, so courteous drivers take it in turn. But the traffic is much heavier in one direction, so it would make more sense for more vehicles from the heavier flow to go through at once. This means pushing on and not taking your turn, but it's considerate to the drivers in the queue behind you. What's the correct hand signal for "I know I look like a rude, pushy bastard, but I'm thinking of the drivers behind me"?