NETWORK LOADING VERSUS EQUILIBRIUM ESTIMATION OF THE STOCHASTIC ROUTE CHOICE MODEL MAXIMUM LIKELIHOOD AND LEAST SQUARES REVISITED*
比较了随机路径选择模型中两种估计方法：网络加载法会高估旅行成本系数，而均衡估计法无偏且效率略低；随着网络拥堵加剧，加载法的预测误差增大，均衡法则误差减小且效率保持高位。
ABSTRACT Daganzo (1977, 1979), Daganzo and Sheffi (1977), Sheffi (1985), and Sheffi and Daganzo (1980) have used one assumption about traveler behavior in developing estimation techniques for the stochastic route‐choice problem and another assumption in predicting flows on networks by using the same model. In estimation, they calculate the congested travel costs of the network links from observed flows on the network, and the network is loaded based on these costs. In prediction, they follow their stochastic user‐equilibrium assumption by which travelers evaluate costs using the mean of the observed flows (or equilibrium flows). The travel‐cost coefficient obtained from the loading method systematically overestimates the true travel‐cost coefficient from which the observed flow data (which must be used in loading) is generated. The estimates of the same coefficient, obtained in this paper, by constraining the estimation results to conform to the equilibrium conditions are unbiased, and only marginally less efficient (have larger standard deviations). The average percentage error and inefficiency of the link flow predictions based on the loading method increases as the level of congestion on the network rises. In contrast, the average percentage error of link flow predictions based on the equilibrium estimation method declines and their efficiency remains very high as the level of congestion on the network rises.