By Ice Road
During winter time an ice road yes! an ice road on the seaconnects the mainland to Hiiumaa.
An ice road differs by letting people drive at quite a high speed with safety belts open. The speed is reduced only while approaching the occasional board- covered cracks. The crossing takes approximately 20 minutes to cover the distance with favourable conditions. You can even pass the ferries that "drive" on the next lane!
By bus
While planning the bus trip one should keep in mind that despite of Hiiumaa being so small, still not all the buses are heading to Kärdla, some are going along the southern part of the island to Käina and Emmaste. The schedules can be found at Bussireisid.ee (http://www.bussireisid.ee).
By ship
Mostly people come to Hiiumaa by ferries, either from Rohuküla on mainland to Heltermaa or from Triigi in Saaremaa to Sõru.
Saaremaa Shipping Company (http://www.laevakompanii.ee) takes passengers onto Rohuküla-Heltermaa, Rohuküla-Sviby and Triigi-Sõru by ferries with shops, bars and restaurants and other places on board. The trip lasts 1,5h. You can choose between the shop, bistro and bar. Tickets can be booked 30 days in advance.
The smaller ferry "Kõrgelaid" is sailing the Sõru-Triigi route. The ferry is small and more ascetic but the trip lasts only 60 minutes. No sailing on during severe ice condition in winter-time.
By plane
The quickiest way to reach Hiiumaa is by air. The regular flights between Tallinn and Kärdla are operated by Avies (http://www.avies.ee) six days a week no flights on Saturdays and all the year round. It takes 35 minutes to fly from Tallinn to Kärdla and there is a bus waiting the passengers at Kärdla Airport.