7.1.1 Discussion of the findings of Thesis 1
The findings of Thesis 1 are consistent with previous studies of the literature, for example, AVs increase the VMT, replace more than one conventional vehicle, and decrease the trip time.
The magnitudes of the VMT and the reduction in the trip time are different than in previous studies due to the varied factors, such as the locations of the activities, the road, and public transport network. Compared to previous studies, the findings of this research reveal some new results, such as the alteration of modal share, when the VOT of travelers changes from 100%
up to 50% of the VOT of conventional cars. The study finds negligible changes in the modal share when the VOT of travelers is less than 50% of the VOT of conventional cars. It can be derived from the obtained results that using AVs reduces the travel time. The amount of reduction depends on the fleet size of AVs (i.e., smaller AVs fleet size means longer trip time and larger waiting time), the travelers’ (i.e., group of users) characteristics, and their plans (i.e., the locations of activities, the transport mode, and the activity time).
The indirect consequences of using AVs can be realized from this study. AVs decrease the travelers’ travel time based on their locations and destinations as well as the traffic condition, which is affected by the time of traveling during the day. The decreased number of vehicles on the street and the reduction in using the parking spaces influence the price of properties in urban
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areas and convert many parking spaces to serve other purposes, such as public spaces. Budapest is classified as a historic city, where a lot of buildings do not have parking garages, and widening the streets is not a solution to satisfy the increasing demand. Moreover, taxes and fees should be applied to parking and driving to discourage people from using cars in the city center. AVs provide a solution for the problems of parking areas and narrow roads as well as might motivate people to reshape the existing urban land use.
Different groups of users are selected based on the benefits that they can obtain when AVs are on the market. Each group is divided into one or more scenarios based on the definition of the group and the collected data. The impacts of AVs on the travel time of the different groups as well as on the modal share of each group are not the same. This highlights the importance of these groups in developing various transport choice models. Moreover, separate policies, services and products can be applied for each group based on the relevant developed models.
7.1.2 Discussion of the findings of Thesis 2
Using P&R facilities depends on the travelers’ preferences. It is demonstrated that using P&R systems increases the overall travel time compared to traveling exclusively by a conventional car (i.e., the existing condition), but efficiently managing the parking in the city center can be done by using the P&R system. The results demonstrate that using AVs as a transport mode impacts the existing modal share concerning the VOT of AVs and conventional cars. AVs can attract travelers and make them avoid using the P&R system, which reduces the number of conventional cars and the area needed for P&R facilities. All of these are controlled through the parking pricing strategies set by the decision-makers. Moreover, simulations for multiple scenarios based on different new locations of the P&R facilities are helpful in impacting the traveler’s choice.
7.1.3 Discussion of the findings of Thesis 3
To mitigate the negative impact of the travel time, travelers are predisposed to multitask on board while traveling. Onboard multitasking minimizes the disutility of travel time by converting a part of the travel time into a productive time. People’s preferences determine how the travel time is utilized. In this thesis, the travelers’ behavior on board of CTMs and SAVs is examined. The factors that affect onboard activities are found. Furthermore, the factors influencing the usage of the travelers’ carried tools and those that negatively affect the travel time and the acceptability of SAVs are identified, too. Besides, it is demonstrated that SAVs are preferable over CTMs based on the multitasking availability. The most important factor that makes a negative impact on the travel is waiting time, which may influence the use of SAVs in the future, too. Therefore, decision-makers can influence people’s movements by focusing on reducing the waiting time, alleviating the congestion, and increasing the comfort level. Besides, to attract people, these factors should be considered in case of AVs, too.
Moreover, people’s acceptability of SAVs is examined based on different dimensions, such as the type of the companion, the internal design of SAVs, the provided services, and the potential to multitask on board. The results of the analysis show that the seat availability and the extra tools inside SAVs encourage people to accept SAVs as a transport mode more than other factors, such as the privacy, the travel time, the minimization of the travel time, and onboard multitasking availability.
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Productive travel time contributes to the reduction in the disutility of travel time. This thesis discusses the influence of the travelers’ onboard activities and the tools carried by travelers on the perceived trip time. An investigation on the different possible onboard activities and the tools carried by travelers is accomplished. Therefore, the new way of introducing onboard activities with the tools carried by travelers is examined across the groups.
The results reveal the impact of the tools carried by travelers and onboard activities on the perceived trip time in urban areas across various groups of travelers. The perceived trip time is enhanced when travelers use the carried tools during their traveling to the main trip purposes in urban areas. The tools that travelers carry determine the onboard activities. Travelers prefer a specific transport mode over others when they want to conduct a specific activity. A consensus is revealed about the importance of onboard activities and carried tools in the perception of trip time. Thus, travelers seek to increase their utilities by involving themselves in productive activities on board. Providing an appropriate environment on board, where travelers can increase their utility by involving themselves in multitasking, is required to avoid unpleasant journeys. The ease of use of the tools that travelers carry as well as their availability impacts the perceived trip time, for example, a classical cellphone is not like a smartphone, which can be used to conduct various activities.
7.1.4 Discussion of the findings of Thesis 4
Travelers set preferences for their daily plans to minimize the disutility of travel time and maximize the utility of activities. Multitasking on board minimizes the disutility of travel time by converting part of the travel time into productive time. Traveler preferences toward cars, AVs, and SAVs are examined, where a transport choice model is developed. During the travel, travelers conduct active and passive activities based on their preferences. Onboard activities affect the travel time positively because travelers can get benefits from involving themselves in productive activities, such as working. The impact of multitasking on transport mode choice is positive, while it is negative in case of the travel time and travel cost. Travel time, travel cost, multitasking, income, and age variables demonstrate various impacts on the transport mode choice. For example, the availability of multitasking increases the probability of choosing a specific transport mode. In conclusion, travelers with high income are more willing to use AVs over SAVs and more likely to use cars than SAVs. Besides, people from the older age group prefer using SAVs more than other age groups. Generally, based on the developed model, travelers demonstrate their willingness to choose AVs over cars and SAVs over AVs to maximize their utilities.
Moreover, transport choice models that combine AVs, SAVs, and public transport are developed. The impact of travel time, travel cost, and multitasking options on the probability of choosing a transport mode is explained. The influence varies across the alternatives, which shows that people differentiate between IR-AVs, SAVs, and public transport when they want to be involved in onboard activities during traveling to the sites of their main activities in urban areas. Each onboard activity shows different effects on each alternative as well as on the trip time and trip cost. Besides, IR-AVs seem to be predominant in urban areas, which leads to an increase in congestion since the individual mode is preferred over SAVs and public transport by the travelers. The developed model studies the added (dis)utility of six onboard activities (i.e., reading, writing, talking, using social media and gaming, eating/drinking, and doing
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nothing) in transport mode choice. The onboard activities demonstrate various effects on the travel behavior across the alternatives. The study highlights the preferences of a group of people in transport mode choice. Moreover, the changes in the impacts of the trip time and trip cost on the travel behavior are analyzed. The results show that people are more likely to choose IR-AVs over other modes, while choosing SAVs has the lowest probability. The effect of the travel time on the onboard activities is higher than that of the travel cost, which indicates that having longer travel time gives travelers more time to engage in multitasking. Reading and using social media affect the choice of a transport mode positively to a greater extent than other activities. The variations on the impacts of onboard activities are demonstrated, such as reading, using social media, and gaming make an impact on the potential transport mode choice more positively than other activities, while writing affects the transport mode choice negatively.
7.1.5 Discussion of the findings of Thesis 5
Solely a few studies cover the implications and consequences of adopting AVs. It is well known that different stakeholders can share similar benefits once PSAV is introduced into the market. In this thesis, various stakeholders’ viewpoints are evaluated based on one type of AVs.
The goal is to encourage the adoption of PSAV as a transport mode in the future. The actors, objectives, and criteria are ranked and prioritized. The results demonstrate that users have the highest weight among the actors. The outputs show different rankings for common criteria, such as “cybersecurity”. Highly ranked objectives and criteria are to be considered for further development, which defines the use of PSAV in the future. Current research presents a ranking for every objective and criterion, which helps policymakers in creating their plans and strategies. It is important to implement this research in the future, where the four stakeholders can negotiate the ranking of their own importance in the decision as well as the realization of the findings. The results reflect the stakeholders’ impacts on adopting PSAV, where after discussions, some modifications might be accompanied. The benefit of this study is to find a common strategy for negotiations among the stakeholders to reach agreements on the output of this study. In case the negotiation is not an option due to the large number or lack of motivation of the participants, either equal weight of the decision-makers might be proposed, or some group weight optimization methods might be applied.