# Layout Model of Bike-Sharing Facilities in the Transfer-Influenced Area of a Subway Station
## 4 Conclusions  
In this paper, based on the quantitative analysis of three competitive transfer modes, including \"Bike-sharing + Subway\" mode, \"Walking + Subway\" mode and \"Bus + Subway\" mode, a generalized travel cost function was established. The results showed that the combined travel choice was mainly affected by travel time, cost and other related factors. Through the two-dimensional spatial clustering analysis of cycling data in bike-sharing, it was found that the K value corresponding to the sum of squares of errors should be less than the inflection point of the curve, and the calculation of service radius of facilities in bike-sharing should be less than 250 m. This paper established a bi-level programming model of bike-sharing facility layout and configuration, and put forward a complete process from the prediction of alternative facilities in bike-sharing to scheme optimization. The heuristic genetic algorithm was used to solve NP-hard problems proposed in this paper. The results showed that the approximate optimal solution or satisfactory solution can be found under the conditions of acceptable memory and time cost, which has certain practical significance. Finally, this paper selected Xinglongdajie Station of Nanjing Rail Transit Line 2 as a research case, discussed in detail the layout and configuration process of bike-sharing facilities in the transfer-influenced area, and conducted sensitivity analysis on key parameters. Based on the bi-level programming model, the solution result of this case was calculated. After optimization, the number of facilities in bike-sharing was 20, and the total travel cost was 30,235 yuan. Compared with the original plan, the number of facilities in bike-sharing increased by four, the number of people who changed to rail transit and bike-sharing increased by 166, the generalized travel cost decreased by 2065 yuan, the facility operation cost increased by 13.6% and the comprehensive evaluation index increased by 0.48. In addition, this paper also found that the multi-objective weight parameter had a significant impact on the overall transfer-ride volume and the travelers who used bike-sharing to transfer to rail transit were sensitive to the single-ride cost. This paper proposed a systematic method of facility allocation and configuration in bike-sharing for the transfer-influenced area of urban rail transit. The results of the case verification showed that the optimization scheme proposed in this paper comprehensively considered the target requirements of transfer-ride volume, transfer cost and overload penalty. This paper may provide a reliable theoretical basis for the layout and configuration of bike-sharing facilities in the transfer-influenced area of rail transit stations. The method proposed in this paper can be applied to the layout and configuration of bike-sharing facilities in other urban rail transit stations. In this paper, in order to simplify the calculation and highlight the key points, only the travel modes with strong competitive relationships, namely, walking, bus and bike-sharing were considered in the analysis of the layout and configuration model. Travel modes such as cars and electric bicycles were not considered. The internal mechanisms and interaction within the facilities configuration of bike-sharing in the urban rail transit transfer-influenced area could be examined from a broader perspective if multiple travel modes can be integrated in later research. If user data can be obtained through additional surveys, such as interviews, then the calibration of the model parameters in this paper may achieve better results. It is worth noting that the case in this paper requires the collection of more updated data in subsequent stages to verify the effects of the optimization scheme. Conceptualization, H.Z. and Z.L. ; Formal analysis, H.Z. and Z.L. ; Funding acquisition, J.C.; Investigation, J.C.; Methodology, H.Z. and Z.L. ; Writing--original draft, H.Z. and J.H. ; Writing--review & editing, Z.L., J.H.