Can a person "hop on - hop off" the train in Italy?

I am not an expert on car rental or train routes/questions, but if you have 3 nights in Siena, then I would spend a night in Orvieto. I really enjoyed my time there! I liked Siena but I really liked the hill town feel of Orvieto.

If it is a Regionale or Regionale Veloce train the ticket is valid on the route for 6 hours from the time it is validated and yes you can hop on and off to your heart's delight as long as you arrive at your destination when the ticket is still valid and you are always moving in a forwards direction - no back tracking. If you have made the mistake to buy Regionale or RV tickets on line with a print out or PNR and print out, the ticket starts at a particular time you have selected and is only valid on that day for 4 hours. Don't do that.

If it is any higher level train than R or RV, you cannot jump on and off with a single ticket. For IC and everything higher you have a reserved seat on each leg, and if you are using a pass you have to pay for that seat. If your train is non-changeable that brings other considerations in your circumstances.

If you feel you'll need more than the 6 hrs allowed on one ticket, then buy separate tickets from Rome to Orvieto and from Orvieto to Sienna. I can't believe it would cost much more to do that and then you wouldn't be limited to the time you could spend in Orvieto.

Just took the regional train to Orvieto, first off it is wonderful little town so rich with history and great restaurants, you should stay the night, hotel Duomo is great. The train tickets are cheap, you validate as you go, the green and white machines are all over the train station, you could buy those tickets as you go, we just took the train back into the Rome Termini this morning. Also there is a hertz and Avis rental right there in Orvieto, so you could do that too.

selcano,

Nigel provided an excellent summary of the "hop on, hop off" options. For a visit to Orvieto on the way to Siena, I'd suggest buying two separate tickets. If using Regionale trains, the tickets are relatively cheap so no reason to use a HO/HO method. Also, as you only have six hours on the ticket from the time of validation, that will limit the amount of time you'd be able to spend in Orvieto. Much better to just buy two tickets.

One important point to mention - you MUST validate your tickets on Regionale trains prior to boarding the train on the day of travel, or you'll risk hefty fines which will be collected on the spot. The same applies to Buses, Metro, etc. in Italy. if using the "fast" trains such as the Freccia high speed or InterCity, you can only use the ONE train specified on your ticket as these trains have compulsory seat reservations. If you board the wrong train, you'll be deemed to be travelling without a valid ticket and again, fines on the spot!

I'd suggest travel by train rather than bus from Orvieto to Siena (IMO). There's usually one change at Chiusi-Chianciano Terme but that's an easy one. When you arrive in Siena, you'll have to take a Taxi or Bus up the hill to the town, as the rail station is located at the bottom of the hill. I try to avoid renting cars when there are good public transportation options. There are some potentially expensive caveats to be aware of with rental cars in Italy as well.

Orvieto is indeed a lovely Umbrian hill town, and would be worth at least one night. Be sure to have a look at the incredible Signorelli frescoes on the ceiling of the Duomo, and also St. Patrick's Well if you have time (an incredible engineering feat in its time).

I knew I would get solid advice and info. from the great folks on this forum. Thanks!!!
More questions to follow.