共享单车投放量的增加，在提高使用便利性的同时，恶化了公共空间的利用环 境，目前很多城市的公共空间被单车挤占，行人的活动受到了影响． 为优化共享单车的投 放密度，避免其无序占用城市公共空间，文中首先选取样本城市实施使用者问卷调查，明 确投放密度与利用效用的关系;然后根据行人交通流特征和人群拥挤事故风险形成的演 变理论，拟合共享单车投放密度对公共空间减少、公共空间利用舒适度和安全性的影响函 数;最后，构建考虑公共空间占用费用的共享单车投放密度优化模型，基于运营商利润、使 用者效用、公共空间占用费用和安全事故隐患率等因素，优化单车的投放密度． 算例研究 表明，通过优化投放密度，可以实现骑行人数最大，满足行人行走需求，降低安全事故发生率． 

The increase of distribution density of shared bicycles raises users’convenience on one hand，while worsens the conditions of public space on the other hand． As in many cities the public spaces are crowded with the shared bicycles and the pedestrians have been greatly affected． In order to optimize the distribution density of the shared bicycles and alleviate the disorderly occupancy of city’s public space，a sample city was surveyed on the users to determine the relationships between the distribution density and users’utility． Then，according to the pedestrian traffic flow characteristics and the evolution theory of crowded accident risk formation， the influence function of the drop density of shared bicycles on the reduction of public space， the comfort and safety of public space utilization was fitted． Finally，an optimization model of the distribution density of the shared bicycles in the case of paid occupancy of the public space was built to determine the distribution density according to the factors such as operators’profit，users’utility，public space occupation cost and the risk of safety accident of the pedestrians． The results of the case study show that by optimizing the density， the maximum number of bikers can be achieved， the pedestrian walking needs can be met，and the incidence of safety accidents can be reduced．