I noticed this sticker on the window of the car I rented today to drive from Steamboat to Denver to get my flight via London to Johannesburg.
(apologies for the quality of the image; due to the slope of the window it was difficult to get a shot without the sunlight behind the subject)
I wish Avis in Australia did this. Sydney in particular is a pain with a rental car because there are toll roads everywhere and all of them are electronic payment only. If you don't have an eTag unit (as you wouldn't as a tourist) there is a process to register online to pay the tolls, but the user interface is lousy and in my personal experience it doesn't actually work; the one time I used it, I received an unpaid toll notice even though I'd registered.