OPTIMAL MODEL OF URBAN RAIL TRANSIT LOOP LINE LENGTH

To effectively contend with the congestion issue in urban development, urban rail transit (URT) has long been one of the priority tasks of most governmental agencies, especially in rapid developing China metropolitan areas. Over the past several decades, researchers and engineers have proposed a variety of planning methods to improve the rail transit rationality and efficiency, among which the loop line is one of heated concerns. Therefore, the primary purpose of this paper is to provide a mathematical analysis model of determining the rational length of loop line in URT. Firstly, the functional characteristics and classification of URT loop line are discussed, and then an optimal model of URT loop line length is put forward based on the relative net benefit. The relation between urban rail transit loop line length and its influence factors are analyzed, including construction cost, vehicles allocation cost, operation and maintenance cost, value of travel time saving and ticket-revenue. Taking those factors as the restraint, the optimal model of rail transit loop line length is constructed to maximize the relative net benefit, in accordance with the structure of loop line. The analysis result shows that the optimal length of loop line in URT is 18.9 similar to 51.3km with the ordinary passenger flow intensity of 1.5 similar to 4.0 million people/(km.d), and such an optimal length is inversely proportional to the passenger flow intensity.