Bus network structure and mobility pattern: A monocentric analytical approach on a grid street layout

This study 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 process of dispersion of their activities that 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 absorb the changes. We compare four base transit network structures: a radial scheme, a direct trip-based network, and a transfer-based system by means of either a complete grid or a hybrid structure. An analytical model is used to estimate the behavior of these structures for idealized monocentric mobility patterns with several degrees of concentration. The purpose is to determine the right range of situations for the applicability of each bus transit structure, and to determine 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.