距離衰落函數之理論與實証分析

The Theoretical and Empirical Analysis of Distance Decay Function

區位接近度的概念是區位選擇的重要指標，而距離衰落函數則是構成區位接近度的主要元素。相關文獻曾以密度函數方式對不同的區位接近度衡量式做實証比較，然缺乏對距離衰落函數來源分析、經濟意義的討論與估計式的研究。本文首先介紹該函數的理論來源與推導過程，包括重力定理與熱力學的最適問題；進而討論該函數的估計方法，包括密度函數方式與重力定理模型方式，最後以台北基隆大都會區交通區的資料分別應用兩種方式估計比較之。估計結果顯示密度函數估計方式會低估距離衰落函數中的摩擦係數；重力定理模型方式的估計結果說明台北基隆大都會區中交通區間的距離每增加一公里，區間的旅次流量會減少百分之二十八。

Location accessibility is the major consideration in location choice, and the distance decay function is a crucial factor in measuring location accessibility. Some empirical studies have compared different forms of location accessibility using density function approach. However, there is lack of both theoretical and empirical investigation of this distance decay function. The purpose of this paper is to fulfill this part. This work first theoretically analyzes distance decay function through gravity and entropy optimization method; secondly, it empirically estimates the proposed distance decay function based on both density function approach and gravity model approach. The estimated result shows that the density function approach underestimates the friction parameter in the distance decay function.