Abstract
The paper deals with the bottleneck phenomenon and capacity analysis of the divided two-lane expressways in Japan, which has not been studied so far, although those of the multi-lane expresswayshave been done sufficiently. It is found from the observed data that (1) the bottleneck phenomenon of capacity reduction from the maximum flow rate just before congestion to that discharged from the congestion queue behind bottleneck occurs on the divided two-lane expressways as similar to that of multi-lane expressways;(2) the capacity reduction for the divided two-lane expressways is largerthan that for the multiple-lane expressways;(3) the bottleneck capacity of the divided two-lane expressways is less than the average capacity per lane of the multi-lane expressways. In additions, (4) the relationship between bottleneck capacity and highway geometric characteristics is studied. Finally it suggests a mechanism of improvement of bottleneck capacity by adding an auxiliary lane upstream of the bottleneck for the divided two-lane expressways.
