Pompeii and Herculaneum in one day?

The commuter light rail Circumvesuviana (think above ground BART in the East Bay) connects Sorrento to the ruins, more or less a 1/2 hour ride from Sorrento. The Pompeii ruins are literally right at the "Pompeii Scavi" stop (NOT "Pompeii", which is another stop) The Herculaneum ruins train stop is Ercolano which is a few minutes down the track closer to Naples than the Pompeii ruins, coming from Sorrento. The Herculaneum ruins are a short walk from the Ercolano train stop. The Pompeii ruins cover a lot of territory while the Herculaneum ruins are small compared to Pompeii. Both are very interesting and both are well worth it and they are on Google Street View Seeing both in the same day should be no problem, but plan on spending a lot of time at Pompeii because it is an entire city, the size of downtown Palo Alto. If you have time between Pompeii and Herculaneum you might consider a bus to the top of Mt Vesuvius, the shuttles hover at the Ercolano train stop. The summit is about a 1/2 mile walk up a fire road from where the shuttle parks and waits for you. It can be chilly up there, like Mt Hamilton.

There is a bus service from Pompeii up to Vesuvius. Because it is a scheduled service you have more freedom to stay at the top as long or as little as you like, unlike the shuttles from Ercolano. http://www.unicocampania.it/index.php?lang=en&center=inside&colonna=turisti&action=vesuvio If I were to do the two in one day. I would go to Herculaneum (Ercolano Scavi station) first, it takes about 50 mins and then to Pompeii (Scavi station) on the way back to Sorrento.

We have visited both in one day. They aren't that far apart although I don't remember how long it took to get between them. We took the train from Sorrento, visited Herculaneum first, then Pompeii. Not only are the two sites extremely interesting, they are also in very different states of preservation because of the differing modes of destruction. I recommend that you find the Discovery channel episode on the eruption and watch it before you go. And a good book to read before you go is Pompeii by Robert Harris.