Japan's large merchant ships are very sturdy, and capable of travelling for many weeks at sea. Ships tend to follow established routes and schedules, because that is the best way to make sure that there will be a load of goods waiting for them when they arrive to collect it. Local craftsmen and merchants work hard to prepare a load of goods for the trip to Edo, since a good shipment can provide as much as half of their yearly income.
The ship schedules also are arranged so that there will be a good chance of having clear weather. Ships generally make the trip through the Japan Sea (the north and west coast) in the summer. Ships travelling to Sendai and other pars of Tohoku, or to Kyushu and Western Japan, usually make the journey in the spring or late fall. Ships travel between Sakai port (Osaka) and Edo almost all year long, but the late summer and winter are the most dangerous times for storms, so there are fewer ships travelling at these times
Each region of the country specializes in a particular type of goods, and some provinces are famous for a particular type of product, such as Hirado pottery, Hakata silk, Tosa paper or Akita lacquerware. Eastern Japan tends to be a source of agricultural products or simple manufactured goods like cotton cloth and soy sauce. Western Japan is the source of more advanced manufactured products, like pottery, paper, silk, needlework and iron products.