StressedDave wrote:My thoughts:
1. None, no time at all - you should be in control of the situation not wasting time wondering if others are going to spoil your original plan.
2. That's not to say that the other vehicle isn't part of the plan. My choice would to be a tad (and I mean a tad) leisurely about getting out for the view so that the other driver has time to appreciate the movement. In general, I find (and FWIW for those who don't know, I work at one end of the road JonT is describing) that if they're going to go, they'll move out once they see you out there if they have any intention of doing so.
3. How 'buried' was the second vehicle? If they're so close that they can't see that it's safe to move out and they haven't seen you move out, then they aren't coming out.
4. I'd consider the need for a warning based on the body language of the car. Just giving one because of the manoeuvre seems pointless - it's like fitting a prophylactic to a marital aid. It might make you feel better but it isn't increasing the safety.
'it's like fitting a prophylactic to a marital aid' - Indeed if there are only two involved I can see your point but in the example given there are three and that increases the risk and the need for extra care