Friday the 13th, while unlucky in America, is usually not so in Italy, although this Friday there will be a transport strike in Rome that will be affecting buses and trams. The bus service disruption will probably be a problem for tourists, with the trams least affecting visitors to the city (since the trams tend not to service areas most frequented by tourists and visitors).
The strike will probably place more use on the metro (underground) and the train system in Rome, so if you’re planning to head out, my advice would be to wait until after “rush hour” as many workers will probably seek alternate means to get to work. Expect more traffic, too, as those who don’t typically drive may be forced to take to the road.
The strike is anticipated to last from 8:30 AM until 4:30 PM. Night service is not guaranteed Friday night and early Saturday morning (with the exception of lines 1 and 2).
If you want further specifics on the strike, check out Repubblica Rome’s web site for more details.