## 4 Review of Studies Related to Sustainability in the Context of Multi-Modal Mobility
### Review of Studies
The model was integrated with a dynamic multi-modal network assignment model to accommodate behaviors of multiple on-demand services. A case study in Singapore based on the proposed framework was used to demonstrate the benefits of the proposed approach. The results indicated that AMoD produces a more efficient service. In addition, parking strategies and fleet sizes have significant influence on user satisfaction and performance. (6) Question: Is there a connection between life course and sustainable mobility for the millennial generation? Results: The decreasing driver licensing and increasing use of sustainable modes in many countries suggest that the millennial generation might tend to more sustainable travel behaviors than previous generations. Whether millennials will continue to adopt sustainable transport modes as they age is an interesting research question. The study [53] provides an in-depth exploration of the connection between life course and mobility of millennials in Sydney, Melbourne and Canberra. The study [53] suggests that the difficulty in finding suitable housing near transit may push millennials into area where sustainable transport is impractical as they approach adult, get married or have children. (7) Question: What is the impact of the COVID-19 pandemic on public transportation? Results: The COVID-19 pandemic had led to devastating economic and social disruption. The pandemic also had a significant influence on transport sector and great impact on transport patterns. The COVID-19 decreased travel, increased health and security concerns, and changed the travel patterns. The impact of COVID-19 pandemic on public transportation is an important research issue. The study [87] focused on the public transportation demands and patterns in Montevideo, Uruguay amid the COVID-19 pandemic. The study encompasses the analysis of trip reductions in Montevideo, the correlation between trip numbers and COVID-19 cases during the pandemic periods, the recovery of public transportation usage, and the correlation with socio-economic indicators. These results offer insight into the travel behavior of citizens throughout the COVID-19 pandemic and pave the way for policymakers and researchers to elaborate mobility strategies and policies. (8) Question: Is it possible to encourage people to make sustainable mobility choices and reduce car dependency/emissions and energy consumption through the development of a smartphone app? Results: Although many cities and countries have been promoting sustainable transport, there lacks an innovative approach to guiding users/travelers to make sustainable mobility choices. In the study [54], a user centered application called GoEco! was proposed to persuade individuals to change their transport modes by exploiting eco-feedback, social comparison and automated mobility tracking. Approximately 150 voluntary users took part in the field test of GoEco! in Switzerland in a period of three months. The interviews with users and an online questionnaire provide insights into valuable future research directions to develop recommendations for similar persuasive apps. (9) Question: What is the impact of sustainable mobility strategies on reducing the use of private vehicles? Results: Many countries and governments are introducing new mobility services and adapting the parking policies to promote sustainable mobility by reducing the use of private vehicles. An important research issue is to study the impact of sustainable mobility strategies. The paper [88] aims to study the impact of strategies on sustainable mobility for a metropolitan region in the Netherlands including Rotterdam and the Hague by employing activity based travel demand models (ABM). The case study finds that the impact due to introducing mobility hubs alone is limited. However, combining mobility hubs with sharing services has the potential to lead to significant reduction in the number of car trips.