"I do wonder if there could be limitations on size and perhaps on location."
From my election campaigns in West Lothian and Endinburgh where I have often been the 'poster boy'* I can't believe some of the locations that the LARGE Northern Irish posters can appear on.
In all the Lothian elections I have helped poster in there are three simple rules by which affect the location.
1) Posters are only allowed on lamposts.
2) Posters are not allowed to be on any lampost that bears any other street furniture (i.e. direction and warning signs for traffic or traffic lights)
3) Posters are not allowed on traffic islands or central reservations.
Just locally I have seen some positioning of posters that causes me some concern, and maybe should have done for the poster teams that put them up. But without local by-laws as clear as those above they haven't thought about the implications of where they have put posters.
Maybe Ian is right that there is a need for a little bit more regulation as to where posters should be allowed, as in the Lothian instructions should be clear enough and meet health and safety concerns. The things is in Northern Ireland there is no restiction as to when they can start going up, many have already been up for weeks and there are still 10 days before polling day. In West Lothian and Edinburgh they cannot be up before 00:01 on the Saturday before polling day and have to be down by the end of the second working day after the result is declared.
* For my Northern Irish readers that doesn't mean by face has been smiling down from them but I was responsible for their being put up and taken down again.