Optimizing public transit service in suburban urbanized areas: A case study of Ningbo, China - Evolution from bus rapid transit to urban rail transit

To optimize public transit (PT) service in suburban urbanized areas according to the dynamic changes in demand during suburban urbanization, and to enhance the input-output efficiency of the PT in post-urbanized areas while promoting suburban urbanization, a new mode of bus rapid transit (BRT) is proposed. The mode emphasizes multiple, high-frequency connections to urban rail transit (URT), based on the principle of long-term optimization. The planning horizon is divided into multiple successive decision sub-periods, and a bi-level model for suburban PT service is developed. The upper model determines the PT service (BRT or the URT) for each segment on the transport corridor during each sub-period with the objective of maximizing social welfare over the entire planning horizon. It also calculates the accessibility of traffic analysis zones (TAZs) and the benefits of the PT within each decision sub-period. The lower model determines the housing locations of the newly added urban population, zonal travel generation and modal splits, as well as passenger flows and travel times for the PT in decision sub-periods. Based on the determined PT service for a sub-period, decision-making shifts to the next sub-period. Through successive multi-period decision, a PT service scheme for post-urbanized areas is derived. A numerical analysis with Beilun District in Ningbo as an example demonstrates that adopting a scheme gradually upgrading from BRT to URT (namely BRT&URT scheme) can achieve social welfare totaling 14.136 billion CNY, a 16.95 % increase compared to constructing URT from the initial stage. This validates that the BRT&URT scheme for post-urbanized suburbs can enhance PT service during suburban urbanization while avoiding the high initial costs and poor input-output ratios of early URT investments.