I thought it was Drop D in most dashboard songs… but what you listed is what I’ve always known as “D-tuning.” I think in a lot of dashboard songs, its drop D, or a half step down, or D tuning.

Almost looks like a “four and twenty,” which is DADDAD, and makes a little more sense (at least to my fingers).
I like “pelican” tuning, too, because it spells DADEAD and looks morbid. dead, hee hee

You are correct that they used DADDDD a lot. Most people will call it “D-tuning” like Perchick said, but I’ve also heard people just sound out every letter (dee ay dee dee dee dee).

There’s a great example of this tuning in “Again I Go Unnoticed.”