Transportation modes in Nepal are of two major types; land transport and air transport. Since Nepal does not have an access to sea, there are no means of sea or water transportation in Nepal.
Nepal is accessible by motor-able roads, for the most part. The roads in the cities, low hills and the flat plains of terai are well developed, and are able to host vehicles ranging from mopeds and cars to big vehicles and 12-wheelers.
There are 15 national highways in Nepal, ranging from 36 KM to 1027 KM in length, with Mahendra Highway the longest. Mahendra Highway runs the entire length of the country, from east to west.
The roads in Nepal are poor by international standard. Basic roads are limited to two or four lanes. Highways are limited to six lanes, with smaller portions at many places. Gravel to pitch to basic cobbles, there are a variety of road structures in Nepal. Due to narrower roads in cities, there are often problems in smooth traffic congestions.
Further full information on the highways can be found at https://en.wikipedia.org/wiki/List_of_roads_in_Nepal
In some city and local areas in the municipalities and developed areas, consists some small and non-motorable roads, limited to only two wheelers.
In the higher hilly region and the Himalayas, roads are non-existent, or very limited, with only small walking trails for accessibility. The reason being the difficult terrain. Major Himalayan and higher hilly regions have STOL airports, which are some of the most scenic airfields in the world, that support twin-engine airplanes. Local traders in these area make use of air transport services often to ferry their goods lower. With helipads and heli-reserved landing spots in many areas, helicopter transfer is the option that gives the most flexibility in terms of accessibility in the high altitudes.