Transportation workers have walked off their jobs across Italy in a dispute over contracts.

The four-hour strike Friday affects buses, trams and commuter trains and involves major cities, including Rome and Milan, with hours varying.

It is causing some traffic disruption. However, unions have said they will guarantee a minimum service in rush hours. Service between Rome’s main Termini railways station and the Leonardo da Vinci airport is also guaranteed.

The strike is taking place a day after conservative Premier Silvio Berlusconi was sworn in. However, transport workers often stage strikes in Italy.