Driving the Croatian coast toward Dubrovnik one crosses a few kilometers of Bosnia. If you've done that can you tell me if the border guards checked rental car papers, or just passports? Our rental company doesn't allow Bosnia but this little strip may be inconsequential. Thanks.
Rick agrees with isailtheseas. Here's what Rick says in his book, Croatia and Slovenia 2007: "Always tell your car rental company up-front exactly which countries you will be entering. Some companies levy extra insurance fees for trips taken with certain types of cars in certain countries. More importantly, as you cross borders you may need to show the proper paperwork, such as proof of insurance, often called a green card. Double check with your rental agent that you have all the documentation you need before you drive off."
My husband and I rented a car last year in Slovenia and traveled throughout Slovenia and Croatia, including the coastal road that briefly cuts across Bosnia. The border crossings between Bosnia and Croatia were inconsequential; nobody ever asked for car rental documents. The road was under major repairs, as in at times we drove on rutted dirt while heavy earth-moving equipment worked right next to us. That was last May, so that section of road should be completed by now. Have a great trip.
Email the Bosnian Embassy in Wash. D.C.
They should be able to tell you.