I've discovered a very interesting link; it appears to be a resource intended for Budget's own customer service reps:

https://www.budget.com/bvr/web/html/...D_Numbers.html

Even more interesting material can be found by clicking the "return to BVR home" link on that page; for example:

https://www.budget.com/bvr/web/html/...promo_log.html
https://www.budget.com/bvr/web/html/..._POWERDRV.html

(The second one gives a bunch of nice coupon codes while also explaining how to "capture the reservation, and ultimately the rental, by making the customer feel that they are receiving a special value and that we care about their business.")

There is also good, detailed information about rental policies around the world, and this helpful guide to staying in shape:

https://www.budget.com/bvr/web/html/...ergocizes.html

Anyway, I found much of it quite interesting and revealing; I don't know how long it will remain open like this, but I highly recommend taking a look.