The best way to park on Nantucket is to leave your car in Hyannis. You can reserve a parking spot at the Hy-Line for $15 per day, but you had better call in advance. Tune your radio to 1610 AM, once you get to Hyannis for parking lot updates. The Steamship Authority has parking on a first come, first serve basis, $12 or $10 depending on which lot you use. But you want to leave yourself plenty of time before the ship sails because if the lot at the terminal is full you will be directed to one of two Steamship Authority lots.
One lot is a few minutes walk away, across from Cape Cod Hospital, and the second is a little further away on Yarmouth Road. You can reach that one via a free shuttle bus.
If you do take your car to the island be prepared to deal with limited parking options. The cobblestoned Main Street and the surrounding streets have free parking, but it is limited to an hour in town and two hours outside town. During the summer season the town hires plenty of seasonal police officers who patrol downtown and you will get ticketed. It’s a revenue stream for the Town of Nantucket.The smart thing to do, if you are shopping downtown or just taking in Main Street, is to use the town parking lot. It is a short walk from town on Washington Street, across from the Town Pier.