[Xaccers]

If it starts to impact the safety of the highway, then the council has a duty to do somehing about it.
Have you actually reported it to the council giving evidence of the impact on safety?
Have you written to your MP giving evidence of the impact on safety?
That's what they're paid for, so make them work for their money.
Course it's much easier to sit back and moan isn't it? Bit like with pot holes, plenty of people will moan about them but few actually bother reporting them, which is why it can take so long for something to be done.

As to how they decide whether there will be an unacceptable detriment to highway safety, it's called a risk assessment.
You really haven't done anything at all about this issue in your area have you?
All you've done is come on here and moan right?
How about instead, if it genuinely is a problem to road safety, contact the council and your MP?