To my knowledge, the riding bollards protecting the 'pedestrian zone' at the south end of Castle Street haven't worked for years. There are still large - but difficult to interpret - signs at the entrance to that section of the street. As far as I can tell, they prohibit access to any motor vehicle except for loading, which is only allowed between the hours of 11pm and 10:30am.
I see motor vehicles on that part of Castle Street oustide of those hours every day. The most frequent offenders seem to be white vans during the day, and cars waiting to pick up passengers - presumably people who work in the area - during the evening rush hour.
I've never seen the restriction being enforced, even when there are police in the area.
What's the point of having the restriction if it's never enforced? Basically, a rule that's never enforced isn't a rule - so they should stop pretending that it is, and take the signs down. If they want people to comply with the rule then it needs to be enforced, and people who fail to comply should be dealt with rather than continually allowed to get away with it.
If the council/police can't be bothered/afford to enforce it it would be better done away with, IMO. Otherwise it encourages a mindset that regards "brief" violations of "unimportant" traffic rules as being unimportant. This is something I see an increasing amount of in the city centre, such as people going the wrong way for a short distance along Hill St/Thistle St when they emerge from one of the lanes either side (which AFAICS aren't one way). It encourages the "I'm just..." or "I'll only be..." kind of excuse that people use to justify selfish behaviour.
If nothing else, I'd be interested in any guidance about the right way to raise this issue with the council.
Edited to add: the reason I posted this today is that I noticed that someone has managed to partially demolish one of the signs, presumably by reversing their vehicle into it. If the council fix it then that would imply that they believe that the restriction is valid. If they don't fix it then it further reinforces that idea that "the rules don't matter" - and further adds to the general degradation of the street environment in Castle Street, which is already showing signs of significant dilapidation eg to the granite 'benches' and bollards, many of which seem to have been damaged by - you guessed it - carelessly driven motor vehicles.