(ANSA) - Rome, October 2 - A 24-hour strike by transport unions caused massive disruption in Italy's cities on Tuesday. The strike, called over the failure to reach an agreement on a contract renewal for workers in the sector, caused the metros of big cities such as Rome and Milan to be shut down. Bus, tram and local train services were slashed. With many people forced to take their cars to get to work, there were lots of traffic jams. Other people were forced to walk or cycle long distances. There was tension in Milan, where commuters tried to force open a gate to catch the last metro before the start of the strike at the station near the city's cathedral while staff were trying to close it. "The contract has not been renewed since 2007 so it's inevitable that we are applying pressure," said Susanna Camusso, the leader of Italy's biggest and most left-wing trade union confederation CGIL. "The government raised taxes to support public transport but that money has never been seen and the service has deteriorated".