To get between island groups, you basically have to fly or sail. Chathams Pacific Airline operates between the major islands, with flights from Tongatapu to 'Eua, Ha'apai, and Vava'u and from Vava'u to Niuafoâou and Niuatoputapu. The flight from Tongatapu to 'Eua is, at eight minutes, said to be the world's shortest scheduled flight. (http://www.chathamspacifi...)
Motorbikes, scooters and cycles can be rented on Tongatapu, Vava'u and Ha'apai. On Tongatapu you can hire a car. There are also taxis. To get around the main island, Tongatapu, Teta Tours and Toni's guest house offer day tours of all the main tourist sights. The speed limit is usually 40kph and this is stuck to by the local drivers. You're meant to also buy a local Tongan driving licence on top of your existing licence before you drive 25 Pa'anga. The roads are good in and around Nuku'alofa but deteriorate the further from the town and the further south you travel.Most cars in Tonga are in a terrible state, maintained on a budget and held together by a combination of 'Western Union' stickers and prayer. The low speed limit helps to keep accidents down. There are buses to various points on Tongatapu from Nuku'alofa although there are no timetables.