Not an easy answer!

At first glance, I was not going to photograph this vanity license plate. It looked like it might have some special secret meaning, but something about it piqued my curiosity.

I thought perhaps I would get lucky and the vehicle's owner would suddenly come out of the grocery store, and I could just ask them what it means. I waited a few minutes, but no such luck.

Google provided quite a bit of help, but it was not an easy search. It provided for an hour or so of sleuthing fun. Kind of like working a crossword puzzle.

It is amazing the "crumbs" that people unwittingly leave on the internet, and in this case there were enough clues (that could be cross referenced) to feel pretty certain I had figured it out.

Read the license plate frame from the top to the bottom, just as if it was a complete sentence. Don't forget to include the license plate in the middle as part of the sentence.

Turns out that the owner is a serious bicyclist, and RMBUYAY refers to a custom built "Rivendell Rambouillet" bicycle which is sold by the Rivendell Bicycle Works of Walnut Creek, California, which is fairly close to San Francisco.