and have blue road signs. Since 1 June 2008 highway users in Slovenia have been required to buy a toll sticker (). This system was investigated by the European Commission that it was unfair upon holiday makers and other non Slovenian users of the highway system. On 28 January 2010, after short-term stickers were introduced by Slovenia and some other changes were made to the Slovenian toll sticker system, the European Commission concluded that the toll sticker system is in accordance with European law. According to the Slovenian Motorway Company Act valid since December 2010, the construction and building of highways in Slovenia is carried out and financed by private companies, primarily the Motorway Company in the Republic of Slovenia (Slovene: , acronym DARS), while the strategic planning and the acquisition of land for their course is carried out and financed by the Government of Slovenia. The highways are owned by DARS. Bus transport The beginnings of the bus transport in Slovenia date back to the early 20th century, when Slovenia was part of Austria-Hungary. The first two bus routes, between Gorizia and Postojna and between Idrija and Logatec, were opened in 1912, with additional four opened before World War I. The length of bus lines was . The transport was primarily organised by the Post Directorate of Austria. After the war, the transport was organised by the Post Directorate of the Kingdom of Serbs, Croats and Slovenes, gradually joined by private operators. The buses, primarily manufactured by Saurer, Benz, and Daimler, were small and could accept six to ten passengers. The total length of bus lines at the end of the mid-war period was . After the end of World War II the bus traffic drastically developed. In 1946 the state ministry of local transport in the People's Republic of Slovenia established the National Bus and Transport Company of Slovenia (, DAPPS). In 1948 the company was reorganised to another company named Slovenija avtopromet (SAP) with branches across the country, some of which were later transformed to independent local bus operators. The bus transport gradually replaced the railway transport and became the predominant means of public transport in the 1960s. The bus lines reached over (1 km/km2), with 26 million passengers altogether. Today the bus traffic is the main means of public passenger transport in Slovenia, particularly in towns. The main bus stations are in Ljubljana, Maribor, Celje, and