The tram lines no. 4 and 6 are the busiest city tram lines in the world, with one of the world's longest trams (54-metre long Siemens Combino) running at 2–3-minute intervals at peak time and 4–5 minutes off-peak. Day services are usually from 4am until between 11pm and 0:30am. Hungarian State Railways operates an extensive network of commuter rail services, their importance in the suburban commuter passenger traffic is significant, but in travel within the city is limited.