The regional company ARST does up to 29 round trips a day between Porto Torres and Sassari (a 30mins journey), from where you can continue to Olbia, Oristano, Cagliari and the other main Sardinian towns. You can also get the red and blue ARST buses to Alghero-Fertilia airport (40mins), Alghero (1 hr 5 mins) and Stintino (40mins). Digitur also operates on the Porto Torres-Sassari line, while Sun Lines guarantees a service for Castelsardo (45mins) and Olbia (3hrs 15mins) from June to September.
The bus stop is in via Mare, in front of the tourist port. You can buy ARST tickets from newspaper stands (edicola) and other shops where you see the company logo. There’s an automatic ticket machine at the Alghero-Fertilia airport. You have to buy Digitur and Sun Lines tickets on the buses.