新重力P中值模型及其在城市综合医院区位决策中的实证检验——以无锡市为例

A new gravity P-median model and empirical test in urban comprehensive hospital location decision making:Take Wuxi as an example

区位—分配模型是实现公共服务设施最适配置的有效方法之一。传统的P中值模型以效率作为导向,采用"邻近分配"规则,不考虑设施容量(规模),难以适应城市综合医院供需之间相互作用规律下适度均衡、居民随机概率式选择和区位与规模同步求解的布局要求。本文尝试以P中值模型为基础框架,在对P中值模型来源及其适用性进行分析的基础上,构建出基于供需双方(居民—综合医院)空间相互作用的重力P中值模型。新模型通过纳入"邻近就医"最大出行成本因子,确保居民至少邻近1所综合医院(保障空间公平);通过追求总加权出行成本最小化,确保设施空间配置效率;通过纳入设施容量规模因子实现设施区位和规模同时求解;通过纳入最小规模因子,保障设施规模效率和服务质量公平。进一步通过无锡市区综合医院空间配置进行实证检验发现:采用新模型优化后,综合医院空间配置更加公平、居民邻近就医更加便捷,且能够实现与社区卫生设施协同布局,使整个医疗设施体系空间布局更加合理。本文构建的新重力P中值模型(模型的变量参数可作适当调整)可用于竞争型公共设施区位决策,为相关设施布局调整或者规划提供决策依据。

Location- allocation model is one of the best methods to find the optimal location of public service facilities. Traditional p-median model takes efficiency as a major criterion and applies the adjacency rule—that is, allocating the residents of every demand site to the closest facility, neglecting difference in facilities＇ capacity（scale）. Hence it is difficult to adapt such model to certain distribution requirements of urban comprehensive hospitals that are moderate equilibrium—residents select comprehensive hospital stochastically with certain probability and location and capacity calculation of the facilities should be solved synchronously due to the spatial interaction between supply and demand. In order to address this type of location-allocation problem, we take the P- median model as the basic framework and discuss the development and applicability of the model,then construct a gravity P- median model based on the spatial interaction between the residents（demand） and urban comprehensive hospitals（supply）. The new model makes some improvements in a number of aspects.First, spatial equality, that is, all residents can conveniently reach at least one comprehensive hospital, can be ensured by incorporating the highest travel cost（from the demand site to the adjacent hospital） factor. Second,spatial allocation efficiency is guaranteed through the pursuit of minimizing total weighted travel cost. Third,facility location decision and scale configuration are solved simultaneously by incorporating a facilities＇ capacity factor. Fourth, facility scale efficiency and fairness of service quality are ensured by incorporating the minimum scale factor. Furthermore, through the empirical test in Wuxi City comprehensive hospital spatial configuration, the new model is validated and considered effective and practical. After optimization using the new model, compared with the current distribution the new spatial allocation of urban comprehensive hospitals is more equitable and more convenient for residents in the service areas to access; the collaborative distribution of comprehensive hospitals and community health service institutions can be achieved, and therefore the spatial distribution of the health facilities is more reasonable. Instead of practical applications, this study focused on the theoretical approach of model building, so some parameters need to be adjusted based on the supply and demand change when such model is applied to practical planning. It should be noted that such new model gives a relative optimal distribution result, which can support certain decision making for future public facility distribution adjustments or new town construction, meanwhile enrich research on public facility location allocation both in China and abroad.