Citation

Kang N, Nakamura H. Transp. Res. Rec. 2015; 2517: 61-70.

Copyright

(Copyright © 2015, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/2517-07

PMID

unavailable

Abstract

At roundabouts, the main streams that conflict with entry flow and have a significant effect on entry capacity are circulating flow and pedestrian flow. Pedestrian impact is estimated with an adjustment factor (fped) in existing methods that were developed under standard roundabout designs, such as a physical splitter island at entry and exit. However, available space may limit these geometric designs in some locations (e.g., in Japan), and, as a result, the impact of driver and pedestrian behaviors on entry capacity probably changes. In a microscopic approach, entry vehicles cross pedestrian flow through available pedestrian gaps. Therefore, gap acceptance behavior is used to reproduce conflict with pedestrians. This analysis aimed to estimate roundabout entry capacity that considers conflict with pedestrians by gap acceptance behavior as well as several influencing factors, including presence or absence of a physical splitter island and the farside pedestrian yield rate (i.e., number of drivers yielding to the total farside pedestrian demand). Entry capacity was estimated two ways, with simulation analysis and a theoretical model. The estimated entry capacity results from the two approaches were compared, and the limitations of each approach were interpreted.

RESULTS from the two proposed approaches also were compared with those from the existing fped model that was applied in Highway Capacity Manual 2010 (referred to as HCM fped).

FINDINGS imply that HCM fped is not appropriate for Japanese situations. Both proposed approaches are expected to be used in the planning and design stages for roundabout implementation not only in Japan but also in other countries that must consider space limitations and pedestrians.