Design scheme of multiple-subway lines for minimizing passengers transfers in mega-cities transit networks

The integration of subway and bus networks has become an effective solution to reduce the growing congestion. This study presents a practical scheme of multiple subway line design to obviate the difficulty of dealing with large-scale networks that always suffer from severe combinatorial problems. The new lines are aimed to increase the overall transit network efficiency. A mathematical formulation is derived to minimize passenger transfer number (PTN) among public transportation facilities. A real case network of Greater Cairo city is used to validate the presented methodology. An algorithm is designed to optimize the number of needed transfers between stations. The analysis includes a multi-subway evaluation of three categories to identify the optimal solution depending on PTN variance and direct trips percentage. After testing many solutions using the brute force technique, two subway lines are recommended with their station structure to increase the overall network connectivity by more than 70%.