01046110

Component

Large-scale expressway constructions have recently arisen in Shanghai and many other Chinese big cities in order to cope with rapid growth of traffic demand derived from violently erupting motorization and urbanization. One of conspicuous features of Shanghai expressways is that most of basic expressway segments are influenced by nearest bottlenecks due to dense-ramp layouts, frequently changing number of lanes, and heavy traffic volume during peak period in central districts. The paper makes attempt to probe the location effects of bottleneck on speed-flow relationship, which have been insufficiently underscored during past decades. By examining consecutive-five-weekday median lane data collected by inductive dual-loop detectors of one expressway in Shanghai inner area, integral speed-flow relationships including upper segment, congested segment and capacity area, are obtained from six sites. The further analysis on those sites within same basic expressway segment unveils that it is the movement of upper and lower segments of the speed-flow relationship that produces the integral curve. The right end of upper segment gets a speed increase with the site farther to its upstream bottleneck, whereas the lower segment gets a speed drop with the site closer to its downstream bottleneck. The movement features accord with general driver behaviors of discharging or approaching a bottleneck. The visible effects of bottleneck on the movement of two segments last for at least 600 meters on the expressway. The factors intensifying or weakening the movement features are also identified. The conclusions probably result in a better understanding of the congested traffic flow characteristics.

01042056

07-1058

English

18p

2007

Transportation Research Board 86th Annual Meeting

CD-ROM

Figures; References (12)

Bottlenecks; Expressways; Highway capacity; Highway travel; Traffic; Traffic congestion; Traffic flow; Traffic speed; Travel demand; Urbanization

Shanghai (China)

Design; Geotechnology; Highways; Operations and Traffic Management; Planning and Forecasting; I21: Planning of Transport Infrastructure; I72: Traffic and Transport Planning

Transportation Research Board Annual Meeting 2007 Paper #07-1058

TRIS, TRB

Feb 8 2007 5:40PM