## 5 Discussion
### Comparison with Existing Empirical Studies and Best Practices  
When comparing our findings with existing empirical studies and best practices, we observe several points of convergence, as well as areas where this research either diverges from or contributes beyond the current literature:  
* Convergence with best practices:
* Mixed platform (\"Spanish Solution\"): Our conclusion that a mixed-platform configuration tends to outperform either a central or lateral platform aligns with experiences in cities like Barcelona and on some lines of the Mexico City Metro, where the so-called \"Spanish solution\" is used to reduce door conflicts and shorten train dwell times. Empirical observations in these systems support the idea that physically separating boarding and alighting flows lowers congestion both on the platform and at the train doors;
* Use of the level of service (LOS) scale: By employing [PERSON]'s framework to measure pedestrian density, we align with the quality-of-service assessment methods widely adopted in various transport systems. Many metro operators apply density-based indices, so our findings regarding LOS thresholds are consistent with well-established station design practices. * Contributions and divergences:
* Phased or modular construction: Our study goes beyond many empirical investigations by proposing a modular growth strategy: starting with a central platform and later adding lateral platforms to achieve a mixed design. Although there are isolated instances of stations that have been urgently expanded in an ad hoc manner, few studies systematically describe how to carry out such a progressive and controlled expansion. In this regard, our work deviates from the common approach of static or single-phase station design. It enables planners and designers to build stations with reserve capacity so that, when facing an unexpected future surge in demand, they can increase the station's capacity--effectively doubling it--without replicating the entire structure;
* Analysis of asymmetric flows: Many empirical studies concentrate on station performance during relatively symmetrical peak hours, but they do not always explore situations characterized by high levels of asymmetry. Such asymmetry is quite common in stations located on the outskirts of cities, where the flow is predominantly outbound in the morning and inbound in the afternoon. Our research emphasizes how certain station types respond to markedly unbalanced demand. This focus highlights a gap in best-practice guidelines, which generally address \"bidirectional\" peak-hour surges rather than flows concentrated in one direction (due to specific events or other factors). This contribution is valuable for planners, as it enables more efficient use of available space and resources. By contrasting our results with operational data from real stations and recognized industry standards, our proposal provides a comparative lens through which to better understand the advantages, limitations, and opportunities for improvement across different platform configurations. Furthermore, we encourage additional empirical validation--especially in stations recently expanded or those facing highly asymmetric demand--so as to strengthen the practical value of a phased or modular strategy in metro platform design. Therefore, the method employed in this work is appropriate for several reasons:* Comparative approach: Our aim was to analyze three platform configurations (central, lateral, and mixed) under different flow scenarios.