The Potential of Demand-Responsive Transport as a Complement to Public Transport: An Assessment Framework and an Empirical Evaluation

Demand-responsive transport (DRT) services (collective on-demand services, such as shared ridesourcing and microtransit) offer a collective flexible travel alternative that can potentially complement fixed transit (FT). The combination of an on-demand and line-based service holds the promise of improved mobility and increased service coverage. However, to date, it remains unknown whether DRT services deliver these much anticipated improvements. This study presents an assessment framework to evaluate the performance of DRT and related changes in accessibility, and performs an empirical analysis for a recently introduced DRT service in the Netherlands. The framework includes a performance benchmark between DRT and FT based on the computation of generalized journey times of the DRT rides and the FT alternatives, and can help identify whether DRT is used as a complement or a substitute for FT. The framework covers the spatial and temporal dimensions, and the explicit consideration of rejected trips is an integral part of the evaluation. Results suggest large accessibility improvements for DRT users, especially for some underserved origin–destination pairs. Reducing car use is high on the agenda for transportation planners, yet the flexibility and convenience that the car provides often makes it a more attractive alternative than traditional fixed transit (FT). To compete with private car use, line-based FT could benefit from embracing new flexible services that have appeared in urban areas so as to improve and complement its services. Specifically, demand-responsive transport (DRT) services (collective on-demand services, such as shared ridesourcing and microtransit) could potentially complement FT in urban areas. Even though DRT services are not a new innovation (they were recommended for future urban transportation in the sixties [1]), only recent technological advancements have enabled their real-time large-scale operation. As a result, new urban DRT services have appeared, both in the United States (e.g., Bridj, Lyftline, UberPOOL, Via) and in Europe (such as Abel in Amsterdam, Kutsuplus in Helsinki, Padam in Paris, and Radiobus di Quartiere in Milan). To better understand the utilization of these services and the role they play in relation to FT, a systematic assessment framework is proposed in this study. Several studies have aimed at helping planners design DRT systems. These studies help estimate the required capacity for a given level of service and the resulting operating costs (2), or assess whether DRT should substitute FT for a given scenario (3, 4). Research has also evaluated via simulation the impact that DRT services would have in real urban networks such as in Hino (Japan) (5), Lisbon (Portugal) (6), and New York City (United States) (7). However, little is known about how these services perform in real settings. A notable exception is Kutsuplus, “apparently the world’s first fully automated, real-time demand-responsive public transport service” (8), which operated between 2012 and 2015 in Helsinki, and for which a final project report is available. However, despite Kutsuplus being implemented as part of the public transport system, its final report does not include an analysis on the extent to which the new service improved the mobility in comparison to the already existent alternatives. This study fills this gap by introducing a DRT assessment framework that analyzes the improvement in mobility that a DRT system adds to the transportation network based on empirically observed usage patterns. Current DRT assessment frameworks contemplate the concept of DRT at a high level without including concrete indicators (9), or focus on key performance indicators (KPIs) that consider DRT in isolation from other modes (10). In this study, the accessibility gains (i.e., the increased easiness of reaching the required or desired activities [11]) that DRT granted for the performed trips are examined. The main objective of this study is to help transportation authorities in assessing the improvement in mobility that DRT users have experienced in relation to the co-existing FT alternatives. After a detailed description of the framework, it is applied to a DRT system in the Netherlands. Based on the observed results, the impacts of DRT as a complement to FT are discussed