Study On The Capacity Of Quasi-six-lane Expressways

With China's rapid economic development, traffic demand has been dramatically increasing, and the capacity of many early built expressways are now insufficient, thus cannot meet the development demand of society and economy. Therefore, in some plain area, the original four-lane expressways have been turned into the so called Quasi-six-lane expressways, which remain the original roadbed width. In this process, the central reserve is compassed and harbor emergency lanes are set in order to change the hard shoulders into carriageways. By studying the capacity of Quasi-six-lane expressways, we can measure the increased level of capacity. Thus, it is practical and forward-looking.In this paper, the capacity of Quasi-six-lane expressways is studied. Bases on the analysis of its section features in alignment, a comparison is done among Quasi-six-lane expressways, the standard four-lane expressway which is of the same roadbed width and the standard six-lane ones. It is found that the occupancy ratios of each Quasi-six-lane expressway lane are of great difference, and the capacity of the Quasi-six-lane expressway doesn't increase linearly according to the increasing of lanes. So, based on the on the basic process of highway capacity analysis, the paper analyzes the traffic parameter, which are relative to capacity, such as drivers, passenger car equivalent and flow. By analyzing these parameters, and referring to the case study, it studies the vehicle classification method, passenger car equivalent and calculation formula of Quasi-six-lane expressway as well. Later, in a case study, which is based on the actual survey and the research result, the capacities of Quasi-six-lane expressway, standard four-lane and six-lane expressway are studied respectively, as well as the difference between Quasi-six-lane expressway and the other two. The result can be used as reference and basis of engineering practice.