Rome is a huge city. If you looking for the efficient public transport of any European capital city and you plan to move around the city with them you can also avoid coming to Rome.
Rome’s public transport ( A.T.A.C ) has for years been in a state of heavy abandonment. Inefficient, dated, malfunctioning, reduced, with no air-conditioned (and summer here is very HOT): Roman buses are famous for their inefficiency. No one pays the ticket, they are always overcrowded and have no preferential lanes where to march fast.
They are infested by boaters, molesters, drunkards, and often catch fire!
There is no better way for underground transportation: Only two lines, with wagons that are constantly broken, accidents, slowdowns, strikes and our dear buffers who have control over all the central stations. Barberini, Spagna, Manzoni, Colosseo, San Giovanni and Termini Station AKA “the Nightmare” are the most affected by the crime phenomenon. Avoid turning with large amounts of money and important documents. Be very careful when climbing in the central stations when crowding because it creates fertile soil for thieves.
My advice is to use the Car sharing service: Car2go, Enjoy, or ShareNgo. You will save a lot of money, time and you will have the serenity and security to move freely (you can also go with these machines in the centrum) as well avoiding scams from various illegal taxis.