travel between Civitavecchia and Sienna

This can be done by Regionale train. These are the cheapest and slowest trains as they make every stop. But unusually, there is a run from Civitavecchia to Siena via Grosseto that is both the fastest, cheapest and fewer train changes - just one. You can seem to pull this run up on Trentialia because they are trying to send you to either Pisa or Rome/Florence. If you write things down and hand it to the agent, you can get these tickets. Here's a link to what I see on the German train website. I can see it as well on Trenitalia. If you take the Regionale trains all the way, the fare will be 11:55E. That's cheap for a ride of almost 4.0hrs. Oddly, there are a few runs with high-speed trains to Grosseto but overall, it's more expensive and they won't get you there any faster. First, here's a link to what I see on the German Railsite. http://gyazo.com/5cce53ad24776ae0ec5e6256b502d0d0 Second, here's a link to what I see on Trenitalia. http://gyazo.com/a52ad1b80adb6b1f0130334c89ffb4d6

Probably not. What solutions does trenitalia give you? Without checking schedules, there are trains north along the coast but you probably have to change in Grosseto. Probably regional trains with a couple of changes. Again, without checking schedules, I assume it would be faster to go through Rome/Termini and then on to Sienna. But you can find that out for yourself at bahn.de for just scheduling information or trenitalia.com for routes and fares.

Don't rule out taking the bus instead of, or in addition to, the train. The bus station in Siena is right downtown, but the train station is a couple of miles.