Sardinia is about 270 km (167 miles) long from north to south, which takes 3–4 hours to drive on main roads; it's roughly 120 km (75 miles) across. Most of the ferries that connect the island with the mainland transport cars.
Roads are generally in good condition, with clear signposting. Superstrade double-lane routes are well developed. Expect winding inland mountain and coastal roads with hairpin turns. Most gas stations are closed in the afternoons, at night, and on Sunday, though at those times you can still use cash to automatically gas up. Try to avoid driving at night, when mountain roads are particularly hazardous and roadside facilities are infrequent, especially in the east. Fog may be an issue in winter.