Essentially where
"rights of way" are concerned, you're also expected to be prepared for vehicles joining the carriageway/junction.
So, at a t-junction onto a fast A-road, if someone pulls out and you hit their front
(b-pillar forwards), then they're pretty much automatically at fault
- because they will have appeared to be stationary for a reasonable amount of time.
If you hit the rear of their car, then the assumption is that even if they were not fully out of the road, you should have seen them and prepared.
There's always a lot of arguing and conditions you can do and in these cases a lot of what happens is down to how good you are at preparing information/photographs/scientific stuff like length of skidmarks
- and how much of a pain you can be to the insurance firm
- but these are the basic assumptions they tend to work with.
Might not be right, but how many times have you had some dithering idiot pull onto a 60mph road in front of you and had to brake VERY hard to avoid hitting the back end? Logically they're doing something dangerous, but because you'd hit the back of their car then you're basically
"in the wrong"
- partly due to the tendency of people to be crap and lie, and say things like
"I was just driving along and they rammed me".
One of my first rules of driving is that EVERYONE is utterly incompetent and I should presume that whatever the most retarded, illogical and downright dangerous option would be in any given situation is the one that they'll take[1]
.
It's why I give HGV drivers a wide berth
- they keep proving me right!
[1]
Myself included.
My 1st ever accident 
