Bus Operation Status Evaluation Based on Natural Breaks

Abstract:

To overcome the unstable results of bus operation status evaluation among different cities， the Natural Breaks was used to cluster the order statistics of bus travel speeds and determine the critical speed. The optimal classification of the bus operation state was determined according to the Goodness of Variance Fit and its increment. The critical speed， percentile， and ratio to bus free-flow speed are taken as the classification parameters to evaluate their stability. The research results show that： Dividing bus operation states into four categories is a sound choice， corresponding to the congested， slow， smooth， and free-flow states， and three critical speeds， e.g.， congestion， smooth， and free-flow speeds. The ratio between bus travel speed and free-flow speed should be the best parameter to recognize bus operation states. The ratios of the congestion and smooth speeds to the free-flow speed are 1/3 and 2/3， respectively. Taking the ratio between bus travel speed and free-flow speed R_BF as the evaluation parameter， when 0≤R_BF<1/3， the urban bus system is in congested status； when 1/3≤R_BF<2/3， it is in slow status； when 2/3≤R_BF， it is smooth.