I saw the sign.

So, it seems that a street sign is a pretty obvious choice for "Outdoor Directional Type" - but after considering it, I really think that it's one of the better choices. If you look at a street sign, it's a great example of how very simple, and often limited type, is all that's needed to get the job done. In the instance of street signs, the less text used, the better. When driving down the road, you don't have the time to read a wordy sign. So instead, only a few words are used with very recognizable symbols (like arrows). In fact, words don't even need to be used in some cases (like the yellow sign above).