# Physarum-Inspired Bicycle Lane Network Design in a Congested Megacity
## 6 Conclusions  
This paper presented a BLN design to promote green mobility in a congested megacity, employing a bioinspired Physarum method. Taking into consideration existing local routes and avoiding main roads as much as possible in the design of the BLN, the mathematical model of Physarum has been adapted for the case of a congested megacity. The proposed model is applied in designing two BLNs for the megacity Dhaka, which is considered one of the most congested cities in the world. The first BLN is designed for the most congested and busy central city area. The second BLN is designed for the extended area covering the entire Dhaka city, suitable for eBikes given longer travel distances. The proposed BLNs are shown overlain existing networks (Figures 4 and 7); optimal BLN routes for a given node from a reference node, with distance and estimated travel time, are tabulated (Tables 2 and 5) accordingly. Since the proposed BLNs considered mostly local routes, the travel distances between different nodes on the proposed BLNs are often longer than vehicle routes, which is logical and acceptable. On the other hand, the effectiveness of the proposed BLNs is clearly revealed (Tables 3 and 6) when travel time required on the BLNs is compared with the time required by a car, taxicab, and public bus to travel from reference nodes to other nodes. Finally, the average travel speed, using proposed BLNs, is found economical in terms of mileage, time, and cost compared with public transport (e.g., bus) and is almost its double in peak hours (Figures 5 and 8). Unlike traditional network design approaches that usually consider the shortest routes, the proposed method has obtained both BLNs by avoiding main roads as much as possible. Hence, the proposed BLNs ensure no interference to the city's mainstream traffic. Although BLNs mainly use the local roads, taking slightly longer travel distance in some cases, the travel time using a bicycle/eBike is found shorter than both public and private transport. The proposed Physarum-based algorithm accomplished efficient identification of highly desirable features in its BLNs of a megacity. As BLNs provide the most cost-effective means to promote green and healthy mobility in a congested megacity, it is expected that many users will choose to use the bicycle as alternative transit, to shorten their travel and to contribute to shifting the transportation paradigm of their city. However, the actual implication of the proposed BLNs requires an administrative decision by city authority; thus, real networks, as well as their performance, may deviate due to practical constraints. On the other hand, the city authority may provide better BLN options, undertaking small-medium construction to enhance its design and exploit its benefits further. The current work leads to several research directions from motivational outcomes and limitations of this Physarum-inspired study. This study will be encouraging for designing BLNs to promote green mobility in other congested megacities with sustaining constraints. Bicycle parking spaces and some other relevant options should be adopted with a BLN design for better practical prospects, which have not been considered in the present study. For the megacities having organized public transport services (e.g., metro, rapid bus transit), green mobility approaches integrating BLN with public transport services might be attractive, as well as more effective. Moreover, the modifications introduced to the Physarum-inspired method in this study can open new ways of solving other complex real-world network design problems, such as water distribution networks. Conceptualization, M.A.H.A., M.A.H. and N.S. ; methodology, M.A.H.A., M.A.H. and M.A.S.K. ; software: M.A.H. ; writing--original draft preparation, M.A.H.A. and M.A.H. ; writing--review and editing, M.A.H.A., M.A.H., M.A.S.K. and N.S. All authors have read and agreed to the published version of the manuscript. The APC was funded by M.A.S. Kamal. Not applicable.