Sardinia is about 270 km (167 miles) long from north to south and takes three to four hours to drive on the main roads; it's roughly 120 km (75 miles) across. Cars may be taken on board most of the ferry lines connecting Sardinia with the mainland.
Roads are generally in good condition, with clear signs. "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 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.