I agree that over-reliance on pictograms frequently causes confusion.

I remember reading an article some time ago about European vs North American traffic signs. The article was praising the European system that relies more heavily on icons over the North American system which is more text-heavy. I can't remember the details now, but I remember disagreeing vehemently with the article.

I find many of the traffic icons (particularly the ones indicating something about parking, stopping and one-way streets) very unintuitive. I strongly prefer the text-heavy signage that I see in the US.