It was already told in this area, from 3pm yesterday to 3pm today there are works in Florence around a bridge over railway, locally known as "Ponte al Pino". Unfortunately, the bridge is over the railway triangle joining Santa Maria Novella, Campo di Marte and Rifredi station. The bridge will have to be demolished and rebuilt, today they are installing a temporary walkway over the tracks for the time that there will be no bridge.
This means that today railway connections are severed. If you have to travel from Rome to Milan, you go by train to Florence Campo di Marte, take a bus there to Rifredi and find a matching train in Rifredi to Milan; you will need an extra hour and two changes. SMN station can't be reached from the south. - Railway traffic has been cut to 50%, regional trains end in Campo di Marte and some trains are rerouted through the east coast railway.
You have to stay tuned as this is only the preliminary work. Before the end of the year, seven work days (not necessarily consecutive) like this one are being planned to tear down the old bridge and slide in place a new one. Dates are still to be announced, but you will notice the severe reductions in national railway timetables in some selected days.
UPDATE: RFI (railway track managements) foresee a 96-hours closure in the first week of July, an 80-hours closure in the last week of July and a later additional 12-hours closure to remove the temporary walkway.
To tell all the truth, this week the number of railway passengers was much reduced, a lot of people were hired to help the railway passengers but conflicting infos were reported and people had some difficulties understanding the master plan.