Planning a road trip through the Alps
Austria–Switzerland–Slovenia trip without getting tripped up by 3 different toll systems.

A drive through Austria, Switzerland and Slovenia can take you from glacier-fed valleys to lakeside towns to mountain passes in the space of a single week, and it's one of the more rewarding routes you can plan in Europe. It's also a route where the toll rules change more often than the scenery, which is worth building into your planning rather than discovering along the way.
Three countries, three different systems
Austria and Slovenia both use vignettes, so a single purchase covers you for motorways and expressways for the length of your stay. Switzerland does things slightly differently: it sells one annual vignette rather than short-term options, which means even a week-long visit requires the full-year pass. That's worth knowing before you cross the border, since a driver expecting a short-term option the way Austria offers one can be caught off guard by the price and the format.
On top of the vignette, a handful of Alpine routes charge separately no matter what pass you're carrying. Austria's Brenner, Arlberg and Tauern sections are the most common ones drivers run into on this route, and Switzerland has its own tunnel tolls in places like the Gotthard. None of these are covered by a standard vignette, vignette countries or not.
Building the route with tolls in mind
The practical approach is to sketch your route before you leave and mark where you cross each border and where you'll hit one of the extra-toll sections. It doesn't need to be precise to the kilometre, just enough to know roughly when you'll need a vignette, when you'll need an additional toll payment, and when neither applies. Doing this in advance means you're not working it out at a toll gate with a line of cars building up behind you, which is a genuinely stressful way to realize you're missing something.
Timing matters too
Alpine passes can close or restrict traffic depending on the season, particularly outside the summer months, so it's worth checking road conditions alongside the toll requirements. A route that looks straightforward on a map in July can look very different in October, and building in flexibility for weather or closures is as important as getting the tolls right.