Assessment Of Road Network Bearing Capacity Level Under The Condition Of Mixed Traffic Based On The Travel Time

Road network is a network consists of sections and intersections. Urban road network capacity refers to the maximum motor vehicle travel volume supported by urban road network under the condition of resource, environment, management, service level and other external constraints. The carrying capacity is mainly from the viewpoint of Time and Space Resources to study road network capacity, without considering and response the actual situation of traffic demand in different district, so can only be used as the basis of Land arrangement adjustment in urban planning, but can’t measure how traffic management and control measures work in promoting the capacity of road network when the traffic demand is different. To counter the problems above, we can use Road network bearing capacity levels to evaluate the condition of carrying capacity in present traffic demand. Road network bearing capacity levels refers to the service level of road network when traveler travel with a certain trip mode structure under the constant condition of traffic demand, traffic management control and road network.Traditional evaluation of road network capacity is to Calculated the ratio of travel demand and capacity. In this paper, the author analyzed the existing research and method on the basis of literature about road network capacity. The common research methods include space-time consume method, cut-sets method and traffic distribution simulation method, etc. which discussed road network service level from different perspectives, but each models’ consideration is not very comprehensive since the complexity of transportation system, so their approximate solution can’t in conformity with the actual situation. The main feature of road traffic in china is mixed traffic. in recent years, the existence of travel time budget has been raised and research. Travel time is relative stability, universality, can reflect traffic conditions, and it’s can be surveyed easily. So this paper put forward a method to evaluate the network bearing capacity levels in mixed traffic condition base on traffic time. In this paper, the author analyzed the characteristics of mixed traffic flow and traffic time, respectively. Modeling a evaluation the network bearing capacity levels in mixed traffic condition base on traffic time. In order to calculate the travel time accurately, study the resistance of road section and the road intersection in mixed traffic condition, set up an improved link impedance function and improved intersection delay function, and validated by the road and node data surveyed in Nanning.Finally, the impedance functions were applied and validated in traffic assignment, and the evaluation model was applied to specific case, compared to the survey data of traffic time, the result is satisfactory, which proved the rationality of the method.