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I'm not entirely convinced these things (they're about A4 size and often quite inconspicuous) ARE there to help the grieving (though I think we should respect people's right to grieve in whichever form they wish .... though I do take exception to some roadside memorials that are so OTT they wouldn't look out of place in a municipal park). I sometimes think they're there to annoy the perpetrator of the accident who still travels the same road. For the rest of us, they serve as a salutary reminder to drive carefully and safely cos you never know what may happen round the next bend.
My particular reason for posing the question is that I've recently seen one with the name of a person from my schooldays (over 40 years ago in a distant part of the country) and was intrigued whether or not is was indeed she or another with the same name - the deceased person's age might well have cinched it. So, not really morbid at all, just curious.
The website given in the first answer (thanks!) had no entry for the name, though it would appear it is only an internet service and has nothing to do with the roadside scheme. I'll try to find an opportunity to stop next time I see one of these placard to see if there's any small print!