State Key Lab of Software Development Environment, Beihang University, Beijing 100191, P.R. China.
Sci Rep. 2013 Oct 18;3:2983. doi: 10.1038/srep02983.
The vast majority of travel takes place within cities. Recently, new data has become available which allows for the discovery of urban mobility patterns which differ from established results about long distance travel. Specifically, the latest evidence increasingly points to exponential trip length distributions, contrary to the scaling laws observed on larger scales. In this paper, in order to explore the origin of the exponential law, we propose a new model which can predict individual flows in urban areas better. Based on the model, we explain the exponential law of intra-urban mobility as a result of the exponential decrease in average population density in urban areas. Indeed, both empirical and analytical results indicate that the trip length and the population density share the same exponential decaying rate.
绝大多数的旅行都发生在城市内部。最近，新的数据已经可以用来发现与长途旅行的既定结果不同的城市流动模式。具体来说，最新的证据越来越指向指数型旅行距离分布，而不是在更大的尺度上观察到的比例定律。在本文中，为了探索指数定律的起源，我们提出了一个可以更好地预测城市个体流动的新模型。基于该模型，我们将城市内部流动性的指数定律解释为城市平均人口密度指数下降的结果。事实上，经验和分析结果都表明，旅行距离和人口密度具有相同的指数衰减率。
