Marine traffic engineering is defined as the study of marine traffic and the application of such studies to improvements in navigation facilities and traffic regulation. The authors review recent Japanese work in this field.Since the mountainous terrain of Japan hindered the development of road transport, goods have mainly been sent by ship, from the earliest times until the end of the last century. The rapid economic recovery of Japan after the Second World War owes much to the industrial belt along the coast which may be called the ‘Water Megalopolis’, with more than 70 million inhabitants. Shipping provides the greater part of both interzonal and international transport and consequently there is severe traffic congestion, accentuated by the presence of more than 200,000 fishing vessels.