It is interesting to hear from a racer's perspective that slightly wet roads can be worse than standing water. And that you can see standing water and avoid it at 180mph...very impressive! Our logic is that if it's raining, the riders know because it's on their visors. Rain flag indicates worse-than-obvious rain problems. By far the most common use of LoA is oil on the road....it even used to be called the oil flag. We don't have a cement flag (or coconut shavings flag), but once the oil is dealt with and been ridden over enough to make it safe, the flags come back in.