Bhutan had a total of of roads in 2003, of which were paved and unpaved. Because of the lack of paved roads, travel in Bhutan was by foot or on mule- or horseback until 1961; the trip from the Indian border to
Thimphu took six days. Road construction began in earnest during the First Development Plan (1961–66). The first paved road was completed in 1962. A branch road later linked Paro with the Phuntsholing–Thimphu road, and a jeep track linked
Thimphu and
Phuntsholing with
Jaigaon,
West Bengal. Travel time by motor vehicle from the border to Thimphu shrank to six hours. About 30,000 Indian and Nepalese labourers were imported to build the road with Indian aid when India was bolstering its defence against a potential Chinese invasion. Bhutan also provided labour for the construction work. Another road was built to connect
Trashigang with
Tawang,
Arunachal Pradesh. About of roads were built by the mid-1970s, largely with manual labour. There was a road network in 1989; at least were paved with
asphalt, and were classified as national highways. Despite the construction of paved roads linking the principal towns in the south, mountainous terrain elsewhere makes travel difficult even from one valley to the next. Most roads run in river valleys. As part of the Sixth Development Plan (1987–92), the Department of Public Works (in cooperation with the Indian Border Roads Organization) made plans to construct and upgrade of roads and to extend the road network through Bhutan's five major river valleys by 1992. Driveable roads were not the only important development; as part of the Fifth Development Plan, Bhutan also needed an estimated of
mule tracks to connect the country's 4,500 settlements. Main roads in western and eastern Bhutan are maintained by Dantak, a task force of India's
Border Roads Organisation. Roads in the rest of the country are maintained by the
Bhutanese government's Department of Roads. Much of the country's geology is unstable and there are frequent
slips and
landslides, aggravated by the summer
monsoon and winter snowstorms and
frost heaving. Teams of Indian labourers are housed at work camps in the mountain passes to clear blocked roads. Conditions in the camps are poor, with workers breaking rocks into
gravel on a
piece-rate basis when not clearing the roads. An international aid project is underway to stabilise the worst sections of the road. A major
Japanese aid project aims to replace most of the narrow, single-track bridges with two-way
girder spans capable of carrying heavier traffic. Most freight is moved on eight-ton
Tata trucks, which are often overloaded. There is a network of passenger buses, and the most common vehicle in government and private use is the four-wheel-drive pickup truck. A national driver-licensing system includes a
driving test. Government drivers are trained at the Samthang Vocational Training Institute's driving school (formerly the National Driving Training Institute). The roads have
traffic lights; although a stoplight in Thimphu was dismantled, there are reportedly plans to reinstall it. ==Rail==