In reply to Trangia:
I remember when I was learning to drive, my driving instructor used to often remind me that you were only required to indicate when moving off, pulling over, or changing lanes when/if it would be useful for someone else. (At junctions you are/were required to indicate all the time). I'd typically check mirrors (probably better than I typically do now!) notice there's nobody behind, to the side, etc, then indicate anyway. He'd go mental 'There is nobody around! You do not need to indicate here! It is only when blahblahblah'. My point was that I'd determined it was safe to pull over, and there was no harm in indicating anyway, in case there was someone I was not aware of who it might be useful for. His point was that if there was a chance that there was someone that I was not aware of who it might be useful for then it
wasn't safe to stop (or something like that). I said I didn't agree with him, and the following lesson he brought in an article about it from Driving Instructor Monthly or whatever. I still indicate in situations like that, mostly out of spite.
I have also noticed that it seems that fewer people indicate than they used to. This is mostly an annoyance to me:
1. When waiting to cross a road and ending up waiting for a car which isn't actually going to drive over the bit of road I'm trying to walk over;
2. When cycling, for all the reasons already mentioned;
3. When trying to join a roundabout, as someone else already described, and;
4. When you're in a lane at lights where cars can go straight on or right, and there's a large queue in the other (left-or-straight) lane. If there are two cars at the (red) lights sitting there in the right lane, you can't see the indicators on the front one, and the second one is not indicating. The lights change, the front one goes straight on, as you were hoping to, the second one
only now starts indicating, leaving you stuck behind.
People seem to indicate most regularly when it's useful for
them, where someone seeing which way they're going might let them out or something. I often wonder if it's the 'creep' of what my driving instructor preached; you don't really have to bother unless it's useful for someone, but applied to situations (junctions) where you're supposed to (by law) indicate even if you're the only person for miles around.
I had a chat with my Dad about indicating at roundabouts. He's 70-odd, never indicates at all at roundabouts at any point, and was totally unaware that there might be some conventions/use in doing so.
Finally, a friend of mine has a new Lotus. One of the features he's most pleased with about it is that the indicators don't make any tick-tick noise. This was removed 'as it was annoying'. He doesn't indicate any less. I believe (especially #4, potentially sitting there for a while with the indicators on) may be because of the tick noise. Yes, I know, you might get more people driving for 18 miles on the motorway with their indicator on if they didn't make noises.