Confusion around booking train tickets

Jane,

You don't need seat reservations for any Regionale trains.
Your ticket is valid for 4 hours from the time you chose, and it does not need to be validated at the train station since you booked it online.

Once you're in Italy if you choose to buy Regionale tickets at the train station, then you will need to validate (date/time stamp) them at the machines on the platforms prior to boarding the train.

For future reference, you can book your train tickets directly on trenitalia.com

Enjoy your trip!

Edited to add:
You may be interested in reading this very helpful website as it will explain everything you need to know about train travel in Italy (or elsewhere): Seat61.com/Italy-trains

There are different kinds of trains in Italy. Regional trains do not have/require reservations: get on in your proper class and claim the first seats you want, assuming there are seats.

And yes: no need to try to validate tickets bought in advance. They are good for the assigned time or for any train departing up to four hours later. If you buy paper train tickets at a machine in Italy for a regional train, you do need validate them, because they don't have specific times on them.

FYI, there's no benefit at all to booking regional train tickets ahead of time, other than saving you the trouble of doing it there. Regional trains cost the same to book now as they do 10 minutes before departure. You can also buy them from ticket machines at the stations (though the machines may accept only chip and PIN credit cards; my chip and signature credit cards did not work but my chip and PIN card did). Or buy them on your phone with an app like the Trenit app for Trenitalia tickets.

NON-regional trains like InterCIty trains or Frecciarossa trains are reserved, and the cheapest fares do tend to sell out in advance, so you can save money by buying those ahead of time. You also lock yourself in to those dates/times - it's a trade-off. If you change your plans, want to travel a different day, you may need to buy new tickets. Regional tickets, though - if you wait til near the last minute until you are certain when you will be traveling, you still pay the same price as buying them months ahead of time. And regional trains can't sell out, so you have no risk of not getting on.

Thank you for the replies, that was very helpful!
Another question, I'm noticing that my next destination is faster and cheaper to book on a bus. How far in advance would you recommend booking for then? It is for Rome to Siena on Jan 4 (a Thursday, 2 days before Epiphany).

Another point is, there are no reservations on Regionale trains. They are open to all who have valid tickets. So you should get to Venice Santa Lucia station at least 15 minutes early so you can be the first to board when the train is spotted on the platform to make sure you have a seat. Buying ahead on-line gives you no more right to a seat than some one who bought it on his smart phone 1 minute before departure.

Jane,

Another question, I'm noticing that my next destination is faster and cheaper to book on a bus. How far in advance would you recommend booking for then? It is for Rome to Siena on Jan 4 (a Thursday, 2 days before Epiphany).

You don't mention your itinerary but it makes more sense to travel to Siena from Bologna than from Rome.
Have you considered going to Siena en-route to Rome?

If you're planning to visit Florence, you can easily travel to Siena, via bus, as it's a short 75 minute journey.

I know I didn't provide the answer to your question, however I thought you might consider changing your itinerary.

Do you mind sharing your itinerary, so we can better help you?

Yes, I did consider that (makes more sense geographically), but with the dates we arrive in Venice and wanting to do NYE in Rome, this was what seemed to work best for the amount of time we wanted to spend in Siena.

Jane,
I don't know how much the bus costs but when I check trenitalia, I see that there are tickets as low as €17,30pp departing Roma Termini at 9AM and arriving to Siena 11:59 with one change at Chiusi-Chianciano Terme (6 minute transfer time)

I recently took the train from Siena to Orvieto and had to change at Chiusi-Chianciano Terme, a very small train station, so you'll have enough time to transfer as long as you're ready to get off the train when it gets close to Chiusi's train station.

I just found a Flix Bus that goes from Rome to Siena for 11.90 Euros PP no stops. I'm just curious at this time of year (January), 1. will there be a potential of weather affecting bus travel and 2. is it worth it to book buses in advance as it is for some trains?

Jane,

1. will there be a potential of weather affecting bus travel and 2. is it worth it to book buses in advance as it is for some trains?

I've not taken a Flix bus before so can't really help you with that.
I've taken other buses in Italy and the only thing that is definite is that buses are affected by traffic, unlike trains. I think most people would prefer to travel by train since trains are usually faster than buses.

I don't know how popular this bus is but you could probably book the tickets a few days in advance, or you can certainly book it now for peace of mind.

Bus prices don't usually fluctuate, like train tickets for high- speed trains (Freccia and Intercity)

I looked up the trains Priscilla was talking about. The regional train via Chiusi-Chianciano Terme costs 17.30 Euros - same price now as it would be day-of. So, 11.90 Euros sounds really cheap. Plus, as I recall, the train station in Siena isn't directly in town, whereas the buses drop you off right at the edge of town closer to the center. (I took the bus from Siena to Florence some years ago and remember the RIck Steves recommendation about the train station not being close in.)

I took a FlixBus in Europe (not in Italy) back in May. The prices can go up closer to departure as the seats sell out - if they sell out. [Edit: the bus tickets indeed went up on the bus I booked - cost me a few Euros waiting til the last minute.] For January 4, who knows? Looking for tomorrow Rome to Siena, I see one bus as high as 22.90 Euros - but another as low as 7.90. Could be the cheap bus is almost empty, so they actually lowered prices. The rest of this coming week, the cost is 13.90 Euros. Could be slow for travel in Italy now. In early January? No idea.

You could wait. If the buses all sell out, then book the regional train when you get there - it can't sell out, even if you buy tickets 15 minutes before it leaves. Not the end of the world to do that (get to the station early enough to make sure you'd get seats on the train from Rome though; if that is a busy travel day for some reason, it could be packed and standing-room only). I admit, I do prefer trains to buses, so I might opt for the train even at higher cost and with a connection. But a direct bus dropping you closer to the center might make it easier for most people especially if you have bags.

Flixbus has a nice phone app, too. My Flixbus in Slovenia in May was 50 minutes late arriving and there was nothing at all at Ljubljana's "bus station" indicating bus arrival times. But because I had the FlixBus app, I got notified (twice) of the late arrival, so I knew the bus would arrive eventually. (You can also buy bus tickets with the FlixBus app and show them on your phone - no need to print them out.)