Bust dual carriage way in my books is nose to back traffic
A quite one in my books is gaps where you can easily get in without having to ram the gas hard
This one was busy enough that your partner was waiting to pull onto it for 'sometime'.
Your words, not ours!
The only reason we are discussing how busy it was is because you dismissed somebodies suggestion that the van had positioned himself for a safe acceleration prior to joining. You claimed this was un-neccesary because it was 'quiet'. Yet it's so un-quiet that your partner had to wait for a gap big enough for a car for 'sometime'.
I can't see how this is anything other than her impatiently pushing past the van, who didn't notice her, and then drove into her.
It will go 50/50 which on the face it seems a bit unjust really.