Urban expressways in this paper refer to a type of urban road facility similar to freeways. They are free of any
at-grade crossings with other roads, railways, or pedestrian paths, which are instead carried by overpasses and
underpasses across them. However, this type of roadways differs from freeways in traffic condition and some
geometric features: 1) Urban expressways in many metropolitans are extremely congested and operate through
much of the peak hours at or near design capacity. Take shanghai as an example, the average daily turnover of
urban expressways in
network and the average speed during peak hour is 25km/h (Office of the Fourth Comprehensive Traffic Survey
in Shanghai, 2009). 2) The ramp density of urban expressways is much higher and traffic condition is severely
impacted by merging and diverging traffic from ramps. Besides, there is no shoulder on the two sides and
vehicles involved in a crash could not easily leave the lane before they are moving on. Therefore, traffic
disruption caused by a minor incident may lead to a large congestion on urban expressways and the impact
factors for incident occurrence may be quite different from that occurred on highways or rural freeways.
Urban expressways in this paper refer to a type of urban road facility similar to freeways. They are free of anyat-grade crossings with other roads, railways, or pedestrian paths, which are instead carried by overpasses andunderpasses across them. However, this type of roadways differs from freeways in traffic condition and somegeometric features: 1) Urban expressways in many metropolitans are extremely congested and operate throughmuch of the peak hours at or near design capacity. Take shanghai as an example, the average daily turnover ofurban expressways innetwork and the average speed during peak hour is 25km/h (Office of the Fourth Comprehensive Traffic Surveyin Shanghai, 2009). 2) The ramp density of urban expressways is much higher and traffic condition is severelyimpacted by merging and diverging traffic from ramps. Besides, there is no shoulder on the two sides andvehicles involved in a crash could not easily leave the lane before they are moving on. Therefore, trafficdisruption caused by a minor incident may lead to a large congestion on urban expressways and the impactfactors for incident occurrence may be quite different from that occurred on highways or rural freeways.
正在翻譯中..
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