## 4 Review of Studies Related to Sustainability in the Context of Multi-Modal Mobility
### Review of Studies
Question: What are the determinants of mobility consumers' purchase intentions for mobility products with multi-modal transport modes? Results: To find the determinants for travelers to adopt sustainable mobility behaviors, the paper [52] focused on study of mobility motives of travelers. The authors conducted a survey experiment to collect potential mobility consumers' mobility motives and their purchase intentions for diverse multi-modal mobility products. The results indicate that mobility motives considerably contribute to explaining all purchase intentions. Status, financial, independence, safety and hedonic motives contribute substantially to predicting mobility purchase intentions. 2. Question: How to estimate long-term travel delay in multi-modal systems with different transport modes such as subway, taxi, bus, and personal cars? Results: One challenge in multi-modal transport is to estimate the long-term multi-modal travel delay. This arises from the multiple trips across different transport modes and the uncertainty for transferring from one mode to another in the multi-modal travel. The study [107] focused on measurement of long-term multi-modal travel delay based on a 5-year dataset of 8 million residents from 2013 to 2017 in the Chinese city Shenzhen. It was found that (1) the increase in delay of aboveground system is higher than that of the underground system; (2) the upgrade of the underground system infrastructure decreases the increase in the aboveground system travel delay; (3) the underground system travel delays decrease for region with higher population during the peak hours. 3. Question: How to develop a decision framework for supporting integrated sustainable urban policy design? Results: The requirements of designing environmentally sustainable, economically viable, and socially acceptable urban mobility systems pose challenges in the decision-making processes of cities. The issue is to develop an innovative and collaborative decision framework to support integrated sustainable urban policy design for sustainable urban mobility. In [101], the authors proposed a multi-level decision framework for the design of urban mobility policies based on a multi-criteria resource allocation decisions at different levels. To support decision makers, an interactive scenario-simulation tool was developed. The proposed model was applied to the metropolitan region of Rhine-Ruhr for verification. 4. Question: How to develop an appropriate model to support multi-modal travel planning and implementation of the transportation infrastructures? Results: Combining public transport with other transport modes such as shared and on-demand systems results in increasing options in multi-modal travel, leads to increase in complexity and poses a challenge in planning and implementing the transportation infrastructures. Developing an appropriate model to support planning and implementing the transportation infrastructures is important. The paper [69] focused on the implementation of modality switch points (MSPs) within the road network, where MSPs indicate the locations along the route at which travelers can switch from one transport mode to the next. In [69], a model was presented to allow agents to switch between different transport modes at any time to meet the requirements of versatile, individual, and spontaneous multi-modal travel. 5. Question: How to develop a framework for modeling various facets of (Automated Mobility on Demand) AMoD jointly taking into account the decision making of drivers and the centralized coordinated fleet management? Results: Development of a framework that models mobility-on-demand systemsjointly considering various facets, including the drivers' decision making and the decision making of the coordinated fleet, poses a challenging issue in modeling and simulation. The study [70] addressed this issue by proposing a comprehensive framework within an agent- and activity-based demand model, SimMobility.