Vienna public transport agency Wiener Linien faces fresh pressure after an underground train got stuck in a tunnel for several minutes yesterday afternoon (Thurs).Newspapers reported today that the U2 line train stopped in the middle of a tunnel between the Volkstheater and Museumsquartier stations. It stood still following a power supply outage on the service, leaving passengers trapped in the dark for six minutes.The defunct train was eventually hauled away and replaced which led to significant delays in service on the U-Bahn line operating between Karl’s Square in the city centre (Karlsplatz station) and Aspern Street (Aspernstraße station) in Donaustadt district.Only in November, more than 200 passengers were locked in a defect U4 line train in a tunnel near Schottenring station after a power cut for around two hours. According to Liniens so-called error management guidelines, the evacuation of a faulty train must not take longer than 15 minutes.Wiener Linien came under fire over the incident since the passengers were told they were not allowed to exit the wagons and walk to the nearest station after men managed to forcefully open some of the doors of the train. The company controversially offered nothing but eight-day rider tickets costing 28.80 Euros to the affected customers as compensation.Now Peoples Party (ÖVP) Councillor Wolfgang Gerstl appealed on the city government coalition of Social Democrats (SPÖ) and the Greens to “speed up” in replacing older U-Bahn cars with models of the newer generation.Wiener Linien is owned by the city of Vienna. The provincial parliament supervises its operations. The agency started offering a nonstop underground service on weekends. The change of schedules was adopted after 54 per cent of residents participating in a referendum spoke out in favour of such a reform.Public transport had a share of 35 per cent of overall traffic in the federal capital in 2009, up from 29 per cent in 1993. The number of cars registered in the city has also risen over the years from 543,000 in 1990 to almost 664,000 in 2009. Around 1.7 million people live in Vienna.