Budapest has approximately 1.7 million inhabitants, down from a mid-1980s peak of 2.1 million. Budapest became a single city occupying both banks of the river Danube with the amalgamation on 17 November 1873 of right-bank (west) Buda (Ofen in German) and Óbuda (Old Buda or Alt-Ofen) together with Pest on the left (east) bank. It is the eighth largest city in the European Union.
The city-owned BKV runs an extensive network of surface mass transportation, with a heavy emphasis on bus service. The bus fleet includes 1200 diesel vehicles on 200 routes and 15 electric trolleybus lines. Night service is exclusively provided by buses.
BKV operates 35 city tram lines and five municipal railways into the suburban agglomeration. The Budapest Metro underground railway network is less extensive, including two full-sized metros and the Millennium Underground, a small-sized underground tramway, which is more than 100 years old and was the first underground on the European continent.
Approximately 55% of traffic in Budapest, a city with 1.7 million inhabitants, is still carried by BKV vehicles, with 45% remaining for private cars. During 2003 1.4 billion passengers travelled with BKV. During the last decade of the Communist era Budapest had 2 million residents and the public vs. private travel proportion was 80% / 20% in favor of mass transit.