economy was determined by coal mining. Now, considering the investment volume, car manufacturing is becoming more and more important. The most profitable company in the region is Fiat Auto-Poland S.A. in Bielsko-Biała with a revenue of PLN 6.2 billion in 1997. Recently a new car factory has been opened by GM Opel in Gliwice. There are two Special Economic Zones in the area: Katowice and Częstochowa. The voivodship's economy consists of about 323,000, mostly small and medium-sized, enterprises employing over 3 million people. The biggest Polish steel-works "Huta Katowice" is situated in Dąbrowa Górnicza. The unemployment rate stood at 3.9% in 2017 and was lower than the national average. Transport Katowice International Airport (in Tarnowskie Góry County) is used for domestic and international flights, with the other nearby airports being John Paul II International Airport Kraków-Balice. The Silesian agglomeration railway network has the largest concentration in the country. The voivodship capital enjoys good railway and road connections with Gdańsk (motorway A1) and Ostrava (motorway A1), Kraków (motorway A4), Wrocław (motorway A4), Łódź (motorway A1) and Warsaw. It is also the crossing point for many international routes like E40 connecting Calais, Brussels, Cologne, Dresden, Wrocław, Kraków and Kyiv and E75 from Scandinavia to the Balkans. A relatively short distance to Vienna facilitates cross-border co-operation and may positively influence the process of European integration. Linia Hutnicza Szerokotorowa (known by its acronym LHS, English: Broad gauge metallurgy line) in Sławków is the longest broad gauge railway line in Poland. The line runs on a single track for almost 400 km from the Polish-Ukrainian border, crossing it just east of Hrubieszów. It is the westernmost broad gauge railway line in Europe that is connected to the broad gauge rail system of the countries of the former Soviet Union. Large part of the Upper Silesia conurbation features the Silesian Interurbans, the longest tram network in Poland, and one of the largest in the world. Bus and tram transport in and around Katowice and surrounding cities is managed by the Metropolitan Transport Authority (ZTM) since 2019. Education There are eleven public universities in the voivodship. The biggest university is the University of Silesia in Katowice, with 43,000 students. The region's capital boasts the Medical University, The Karol Adamiecki University of Economics in Katowice, the University of Music in Katowice, the Physical Education Academy and the Academy of Fine Arts. Częstochowa is the seat of the Częstochowa