Trains dominated the Japanese domestic passengers and freight transportation until 70s, but now buses, trucks and cars are major transportation for Japanese.
Thanks to opening of new highways almost each year, whole Japan will be covered by highways soon. Long distance bus routes are not only common during the day but night buses are also used by mostly young Japanese to travel. However, long distance buses are not introduced to carry tourists. For instance, there is no regular bus connection between Tokyo and Nikko. Buses are considered to carry people to where railway network is less developed. Also no businessmen take long distance buses between Tokyo and Osaka.
Another distinguished thing of Japanese highways are there are place where you can rest, dine and do shopping. It is called SERVICE AREA or PARKING AREA(SERVICE AREA is bigger and usually equipped with gas station). Not like in Europe where there is McDonald's or Burger King and gas station together, the dining place in Japanese highways are some like a food court. Service area is also equipped with restaurant which you can order at the table.
Service area and parking area are also equipped with many vending machines, especially beverage vending machines which prices are as same as in the city. Japan's most distinguished matter is that you can buy the same drink any vending machine or stores at same price(except at certain hotels or resorts). Then you can buy souvenir at the Service area. Each Service area are keen on selling local souvenirs which attract people to stop at their Service areas. Therefore not like in Europe, people travelling on highway constantly having rests on the way to their destinations.