I'm with those who think they're okay provided not too distracting. As for what's distracting I'll let the experts in concert with bureaucrats decide that. Or actually as pointed out by someone with reference to the LTA site, it seems like they already have.

If memorials are a problems and I'm not saying they are I suspect the problem is no so much the guidelines, but the problems ensuring people comply with them.

To explain: My first thoughts were we didn't even need guidelines I would trust the common sense of those enforcing them (particularly since I'm fairly sure we already have many general purpose ones). I then changed my mind realising that this is a problem. Not because I don't trust their common sense. But because without guidelines, there would be real reluctance to remove even terribly distracting memorials since it will be spun in to a great evil if the media get's a hold of it. I later read someone confirming this with an example from Campbell Live.

So having the guidelines helps, we still need those involved willing to deal with ones that are clearly distracting and accept the flak. They should offer advice to the those placing the memorials if these people can't find or don't understand the guidelines. Unfortunately in some cases it may be a case of "place it somewhere else".

About advertising signs (or anything else near the road that may be a distraction), remember we do have guidelines for these as well and most of this stuff will be dealt with when it's a distraction. Of course there's always debate over how far to go with potential distractions but you can be sure if McDonalds (random example that popped in to my head) put up a sign violating them and tried to fight the LTA on it, the media response would most likely be 'evil multinational trying to kill people' not 'evil government causing great harm to the poor ordinary person'. (The only example I can recall where the media a big deal, perhaps with a legitimate point, was over signs for the local elections where I remember there were complaints the new guidelines were released too late so many had already had their signs produced some of which weren't compliant.)

Yes of course our roads have problems and these need to be fixed where they can, but that doesn't negate the wisdom of properly monitoring and stopping problems others may create, no matter how well meaning they may be.