Ciao sk3,

Actually a great question! The trams are probably as oblivious to traffic and may get you there a tad quicker than a bus on the same route - because as you say, they have "dedicated lines!" Of course, the metro is the FASTEST alternative if it is going your way. I ride metro, tram, then bus (in that order) if I'm in a hurry. The electric buses are great but they often wind into smaller, narrow streets filled with pedestrians. I've seen both the 117 and the 116 stopped because of the foot traffic in front of them. They just get no respect!

In some parts of town there are dedicated bus lanes - You'll see that Via Tritone and Via Nazionale have bus only traffic in one direction. So does the Colosseo if you're coming from the San Giovani direction! Unfortunately many visitors driving in Rome find this out the hard way when they get ticketed for driving in the bus-only areas, or the bus lanes. In other more residential parts of town, there are segregated bus lanes... often marked by dividers in the road. I've been guilty of "borrowing" them when I'm on my motorino.

I did have a situation occur that exposes one of the weaknesses of the trams. I was on the #8 in Trastevere headed into town and we just stopped. It appears that someone in the tram in front of us had suffered a heart attack. So three trams were stopped, one behind another, as they tended to this individual. The driver opened the doors and ordered everyone off... and we started walking. The trams were shut down for about 30 minutes. So if a tram breaks down, has an accident, or an incident... well, the others can''t go around the issue and the line just shuts down... Same thing happened to me on the metro in Rome once also!

For newcomers to Rome, you might read these links on Riding the Buses and The Rome Metro. Good Luck!