抄録
Traffic priority at roundabout entries has played an important role in the history of roundabouts. When roundabouts were proposed and implemented at the beginning of the 20th century, the importance of the priority rule was not well recognized and the nearside priority rule was applied. However, the smaller traffic volume at that time did not reveal this problem until the increased traffic flow caused a locking-up problem at roundabouts. This was same in Japan where roundabouts were used before the World War II. After the World War 11, offside priority rule was proposed in some countries, and in 1958 this rule was tested on public roads in the U. K. In Japan, a traffic engineer proposed the offside priority rule in 1953, but this was ahnost neglected and roundabouts were removed. After the offside priority rule was made mandatory in the U. K. in 1966, the advantages of roundabouts were well recognized and this type of intersection was adopted in many countries including Australia, France, Germany and others. In this paper, the history of the priority rule at roundabout entries in Japan is reviewed in comparison with those of other countries.
