Abstract
The purpose of this study is to discuss relationships between spatial speed change characteristics, which are one of the traffic jam occurrence causes, and motorway alignments and/or facilities in sag sections. Running car experiments were carried out in section of about 45km of Chuo Expressway. In the running car experiments, speed, accelerator opening, and ruining position were collected. One of the results showed that speed drop in sag sections over long distance in upgrade section in which the traffic jam occurs frequently. The sag detection performance of a driver was high as sag with large algebraic difference in grades. Authors also discussed that a sag section might newly actualize to be a bottleneck after lane increase construction completion in this motorway section.
