When planning a driving trip, one thing to consider is tolls roads.
Google maps is great at telling you where they are, and indeed how to avoid them if you choose to do so.
There are a number of different methods of paying tolls, and each country on your journey may use different methods. Often the simplest method is the drive up booth where you pay to enter a section of road system, a bridge or a tunnel. Another method quite common around Europe is the preauthorised method, with the application of an authorisation sticker to the front windscreen that can be read by electronic camera systems within the toll area.
If you are intending a journey that utilises a toll road that uses the preauthorised method, you will need to ensure that you have the relevant authority in place before you enter. Fines can be high and applied immediately at the roadside, or in certain areas referred to a local court for a hearing. It’s not worth getting it wrong for the little inconvenience of paying the toll.
This website www.toll.eu gives a great coverage of tolls in and around Europe, with guidance on both cost and where to purchase from.