From both Zagreb and Rijeka, the Slovenian border is about a 40-minute drive and about a 2½-hour drive from Zadar and the northern Dalmatian coast.
You don't need a car if you are not planning to leave Ljubljana; cars are, in fact, prohibited in the old city. However, traveling by car undoubtedly gives you the chance to reach remote areas of the country and will also allow you to appreciate the country’s natural beauty. If you’re bringing a car into Slovenia, be sure to buy a highway toll sticker, a vignette, at the border. It’s required to drive on any highway, and fines are steep if you’re caught without one. Short-term stickers are available at most gas stations and post offices. Any rental car hired in Slovenia should already have one.
From Ljubljana a four-lane highway (E61) runs northwest past Kranj and continues—occasionally reverting to a two-lane highway on some stretches—to the resorts of Bled and Kranjska Gora. Lake Bohinj lies 25 km (16 miles) southwest of Bled along local highway 209. The Vršič Pass, which connects Kranjska Gora and Bovec, is closed during the winter. If you want to go to Idrija, Kobarid, or Bovec from November to April, you will have to approach them via the south.
A car is advisable for touring the Karst region. However, parking can be a problem along the coast during summer, when town centers are closed to traffic. And parking in Piran, for example, is restricted to season ticket holders only. The E63 highway connects Ljubljana to the coast, passing through the Karst region en route.