Accessibility Models Based On the Gravity Analogy: In Theory and Practice

The most commonly applied types of accessibility models are based on the gravity analogy. In these models, researchers use different types of resistance factors, but they rarely give any elaborate explanation for their choice of a specific type of factor in their research. Another problem with this kind of analysis is that in many cases, the authors do not describe precisely how they determine the constants for a line of calculations in a given model. Thus, the results cannot be fully accepted since they cannot be reproduced by the reader. Finally, we consider it to be yet another huge problem that the results of the models are rarely compared to the real (for example traffic) parameters, therefore, it is also impossible to detect what would happen if the researcher used a different model. In this study, we tried to line up the most commonly used models, and by enlightening the resistance factors, examine their possible usage and their boundaries through exact Hungarian examples.当前应用最为广泛的可达性模型（accessibility model）均基于引力类比（gravity analogy）构建。在该类模型中，研究者会选用不同类型的阻力因子（resistance factor），但极少针对研究中特定阻力因子的选择作出详尽阐释。此类分析还存在另一类问题：多数情形下，作者并未清晰说明如何为特定模型中的某一计算流程确定常量。因此，读者无法复现此类研究结果，其结论难以被完全采信。最后，我们认为还存在另一项重大缺陷：相关模型的输出结果极少与真实（例如交通）参数（parameter）进行比对，故而也无法探究若研究者更换模型将会产生何种结果。本研究对当前最常用的可达性模型进行了系统梳理，并通过阐明阻力因子的选取逻辑，结合具体的匈牙利实例，探究了各类模型的可行应用场景与适用边界。