Comparison of bus network structures versus urban dispersion: a monocentric analytical approach. Evidences from Barcelona's bus network
- Autores: Hugo Badia Rodríguez
- Directores de la Tesis: Francesc Robusté Antón (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2016
- Idioma: inglés
- Tribunal Calificador de la Tesis: Andrés Monzón de Cáceres (presid.), Francesc Soriguera Marti (secret.), Monica Menendez (voc.)
- Materias:
- Enlaces
- Resumen
This thesis discusses which transit network structure is the best option to serve urban mobility. As a consequence of the evolution of urban form, cities have undergone a dispersion process of their activities. This fact has caused a change in mobility needs in the last few decades. Mobility networks and services should progressively adapt to the new demand patterns, especially the bus transit network, which has more flexibility to reorganize the deployment of resources at an affordable cost. Three base transit network structures are compared: a radial scheme, a direct trip-based network, and a transfer-based system. An analytical model is used to estimate the behavior of these structures for idealized monocentric mobility patterns with several degrees of concentration. This is made atop two street patterns, grid and ring-radial.
The thesis aimed at determining the right range of situations for the applicability of each bus network structure, and providing guidelines about the transit network planning process. It turns out that the best structure is not always the same, and depends on the mobility spatial pattern. A radial network is the best alternative in very concentrated cities; however, a direct trip-based system is more suitable for intermediate degrees of dispersion. A transfer-based structure is the best option when the activities are more decentralized. Nevertheless, the decentralization degree that justifies a specific transit structure is not constant. This degree depends on the characteristics of the city, transport technology and users. The street pattern atop the network is designed also affects on the range of applicability, especially on the cut-off point between direct services and transfer-based networks. However, the different network structures follow the same behavior in front of urban dispersion and changes on input parameters in both street patterns.
The analysis of O-D matrixes gives a first approximation about in which decentralized scenario a city is. Therefore, given that decentralization, the arising question is what network structure is the most suitable alternative for its transit system. Barcelona (Spain) is an instance where a change of bus network structure from direct services to a transfer-based scheme is justified. The analytical network design model is applied to design a transfer-based bus network for this city. The eventually proposed network, called the Nova Xarxa, covers the whole city by 28 corridors. The final design improves the level of service, reducing by 4.12% total travel time for the pre-existing bus demand. However, the new bus network design has an important handicap, a greater number of transfers.
The Nova Xarxa is being deployed in a multiple-step implementation process. It is an opportunity to test the conventional wisdom that states that transit riders are averse to transfers and that consequently bus networks should be designed to limit their number. This thesis examines data from the first three deployment phases of the Nova Xarxa. It is found that the lines of the Nova Xarxa are already carrying more passengers than the old lines they replaced. Furthermore, this demand has increased disproportionately with the number of lines opened for service in each phase, revealing the existence of network effect. At the end of 2015, the percentage of trips that involved a transfer was approximately 26%, and it will reach 44% once the Nova Xarxa is completed in 2018.
