TRAVELING IN BHUTAN
Bhutan knows no trains or domestic flights, so you can only travel by car or bus in Bhutan. The country has a relatively well developed network of roads accessing all major towns. However, most roads are small and badly or not at all paved and unlit. Because of the mountains, steep slopes and deep valleys, the roads know many bends and the average speed of vehicles is restricted to less than 40 kilometers per hour. Steep ascents and descents are typical for road travelling, so you best travel only during daytime. During monsoon and winter months, roads can easily become blocked due to snow or landslides and can take anywhere from an hour to several days to clear, so be prepared that travelling in Bhutan can take quiet some time.
Travelling on a tourist visa, the cost of all transport is included in the price of your trip. Depending on the size of the group, Bhutanese tour operators use Japanese-made buses, minivans or cars. If you travel to central and eastern Bhutan during wintertime (December to February) or monsoon (June to September) a 4WD vehicle is an advantage, and often necessary.
Regarding public transport, the good news is that public buses are cheap. A minibus fare between Thimphu and Paro costs 40 Nu ($ 1), between Thimphu and Phentsholing 120 Nu ($ 3), and between Thimphu and Jakar 202 Nu (4 $). The bad news is that public buses are very crowded and quiet uncomfortable. Daily three or four buses run between Thimphu and Phentsholing, Paro and Punakha. Fares and schedules are all monitored by the Road Safety and Transport Authority.
If you get car sick easily and want some more comfort, another option is travelling with the more comfortable Toyota Coasters, operated by several private operators like Leksol Bus Service and Karma Transport. It costs about 50% more than the minibus fare, but it might be worth it.