Merging sections on Tokyo metropolitan expressways differ very little from uninterrupted road sections when considered in terms of accident rates alone. Merging may be difficult, however, under the following site conditions: (1) the acceleration lane on the merging side is short; (2) the merging interval is short; (3) there is a noise barrier or a grade difference between the main road and the merging side; and (4) the merging section is on a curve, inside a tunnel, or on the passing lane side. Difficulty in merging is thought to occur in item (1) because vehicles on the merging side are unable to accelerate sufficiently before merging, and in items (2) to (4), because there is too little time for merging vehicles and vehicles in the main road to ascertain each other's presence. This is also likely to have repercussions in drivers' feelings of having a close call, and sometimes in disturbance of the traffic flow. Merging support services could include the following: (1) merging support for vehicles on the merging side; (2) support by information provision for vehicles on the main road side. Implementation of type (1) support would require complex operational support such as detection of the following distances between vehicles on the main road side and control of merging vehicle speeds. This support is considered difficult to put into practical use quickly because it also involves vehicle control. On the other hand, if type (2) support were implemented by detection of vehicles on the merging side and provision of that information, it would support the choice of suitable merging behavior by vehicles on the main road side. The Japanese system assigns right of way to the main road side. For the time being, however, the type (2) support by information provision to vehicles on the main road side has been selected for study because it is support on a level of information provision that is feasible given currently existing technological resources. This report will describe fundamental research conducted by a questionnaire survey of needs, the results from a survey of main road merging sections by means of video analysis, and monitor tests conducted using a driving simulator. Then, based on the results obtained, it will propose merging support services.
Abstract