The long ton is used for petroleum products such as aviation fuel. Deadweight ton (abbreviation 'DWT' or 'dwt') is a measure of a ship's carrying capacity, including bunker oil, fresh water, ballast water, crew and provisions. It is expressed in tonnes (1000 kg) or long tons (2240 pounds, about 1016 kg).
Trains between Naples and Sorrento depart once every half hour and take about 55 to 68 minutes in duration. Thus, to get from Rome to Sorrento, you would first take a train to Naples, where you would switch to a Circumvesuviana train down to Sorrento.
Naples airport is the closest airport (see Italy airports map for information). There are 3 airport buses a day to Sorrento and from Sorrento there are bus connections to Amalfi. The closest train station is in Salerno and buses connect it to Amalfi.