All these things that I have done

He works on a karma principle that by letting people in/out at junctions you are storing up rewards for yourself later in your journey. Flaky I know, but in practice we find that more often than not the guy you let in turns off at the very next junction. Obviously this does not apply to people who should have got in lane 200 yards back who were just queue-jumping, you get bad-karma/gullibility points for letting them in.