| 1. |
- Badia, Hugo
(författare)
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Comparison of Bus Network Structures in Face of Urban Dispersion for a Ring-Radial City
- 2020
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Ingår i: Networks and Spatial Economics. - : Springer. - 1566-113X .- 1572-9427. ; 20:1, s. 233-271
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Tidskriftsartikel (refereegranskat)abstract
- This paper extends the discussion about the bus network design in face of the mobility patterns associated with different degrees of urban dispersion. Based on an analytical approach, a comparison of total costs among different network structures is made for a ring-radial city, which is the other most common regular city layout. The results clarify what structure is the best solution for different scenarios of dispersion and city and transport characteristics. Simultaneously, the effect of the street pattern on the applicability of each structure is evaluated comparing these results to a previous research for a grid city. Three basic structures are analyzed: a radial scheme, a direct-trip-based network, and a hybrid structure as a transfer-based alternative. Each structure is dominant for a specific range of dispersion: radial networks for scenarios of high concentration, direct-trip-based systems for intermediate degrees of dispersion, and transfer-based structures when the activities are decentralized. However, constraints on stop capacity modify these ranges. Each structure presents a different distribution of travel time in the transit chain and agency costs that determine the most competitive alternative. In addition, the behavior of the structures and the evolution of costs regarding urban decentralization are practically the same for both street patterns: system costs grow with increasing mobility dispersion, the range of applicability for each structure is the same, and changes in their applicability when main input parameters vary are very similar. Therefore, these results make it possible to generalize about the conclusions obtained independently of the street layout.
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| 2. |
- Badia, Hugo, et al.
(författare)
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Design and operation of feeder systems in the era of automated and electric buses
- 2021
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Ingår i: Transportation Research Part A. - : Elsevier BV. - 0965-8564 .- 1879-2375. ; 152, s. 146-172
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates the impact of vehicle automation and electrification on the applicability of fixed routes and door-to-door services to supply a feeder transit solution in suburban areas. These technologies will modify the current cost structure of the bus system depending on how mature they are, reducing operating costs and increasing capital costs. By means of a continuum approximation model, we evaluate the performance for users and agency of the two feeder strategies in different scenarios of technological development. The results show that automation has the main impact on the applicability between the two feeder alternatives while the effects of electrification are considerably smaller. The future applicability of door-to-door trips reaches wider ranges, although this change is especially significant under some circumstances of technology, service area and users. The expansion of this range is relevant in case the automated bus is mature enough (high reduction of operating cost and low vehicle acquisition price), the areas are small, the trips are short and the value of time is high. However, the results reveal that fixed routes will remain a competitive feeder solution in a wide range of scenarios. We identify that the demand density threshold grows sharply in front of any reduction of agency costs once its value is around 200-300 pax/km2-h. Therefore, flexible services will gain applicability especially in environments that allow reaching this threshold.
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| 3. |
- Badia, Hugo, et al.
(författare)
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Feeder Transit Services in Different Development Stages of Automated Buses : Comparing Fixed Routes versus Door-to-Door Trips
- 2020
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Ingår i: Transportation Research Procedia. - : Elsevier B.V.. - 2352-1465. ; , s. 521-528
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Konferensbidrag (refereegranskat)abstract
- The arrival of automated vehicles could significantly reduce the operating cost of mobility services. This fact has encouraged researchers to propose door-to-door services instead of the current fixed routes. However, a comparison between these two alternatives is required in order to identify when (depending on the development degree of the automated vehicles) and where (depending on the characteristics of the area of service) the implementation of each service is the most competitive solution. This research compares the two types of transit services to supply first/last-mile solutions in suburban areas. By means of an analytical approach, the results show that fixed routes remain the most efficient alternative unless the new technology reaches a certain degree of development that allows a high reduction of operating costs. In this case, the applicability of door-to-door services will significantly increase under certain circumstances: small areas of service, short distance trips and high values of time.
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| 4. |
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| 5. |
- Badia, Hugo, et al.
(författare)
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Shared e-scooter micromobility : review of use patterns, perceptions and environmental impacts
- 2023
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Ingår i: Transport reviews. - : Taylor & Francis. - 0144-1647 .- 1464-5327. ; 43:5, s. 811-837
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Tidskriftsartikel (refereegranskat)abstract
- Recently, a new shared micromobility service has become popular in cities. The service is supplied by a new vehicle, the e-scooter, which is equipped with a dockless security system and electric power assistance. The relatively unregulated proliferation of these systems driven by the private sector has resulted in numerous research questions about their repercussions. This paper reviews scientific publications as well as evaluation reports and other technical documents from around the world to provide insights about these issues. In particular, we focus on mobility, consumer perception and environment. Based on this review, we observe several knowledge needs in different directions: deeper comprehension of use patterns, their function in the whole transport system, and appropriate policies, designs and operations for competitive and sustainable shared e-scooter services.
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| 6. |
- Badia Rodriguez, Hugo, et al.
(författare)
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Modelling of Micromobility (M3) - Prestudy on Knowledge Needs and Usage Patterns : Final report
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the last years, a new generation of shared micromobility services has rapidly proliferated in urban areas. The distinctive characteristics of these services in comparison to previous ones are dockless security systems, electric power assistance and a new device different from bicycles, the e-scooter.These technological advances reduce implementation costs and expand potential demand for these services, factors that made their promotion by private companies easy, reinforced by the lack of regulations on e-scooters.This type of service consists in a floating fleet of e-scooters distributed over a service area wherecompanies conduct several tasks of collection and distribution for device relocation and battery charging. Through the company’s app, users find, unlock and lock the scooters and pay for the service. The spread of these services has opened several questions about their impacts on four main areas:mobility, environment, infrastructure and urban space, and safety. The experience from several cities shows several insights about those issues:Travel behavior▪ The average user is a 30-35 years old man who makes an average trip of one mile and ten minutes long, running at speed below 10 km/h. According to this average trip, scooters provide an intermediate solution between walking and cycling.▪ Temporal distribution shows only one main peak during the afternoon, having more users during weekends, similar behavior as casual bike sharing systems, but different from the global mobility. Spatial distribution shows a similar behavior as the rest of the modes with high concentration in city centers and other attracting zones with high densities and mixed uses.▪ The main trip purpose is related to free time for social or recreational activities, ranging between 30% and 75% of the total rides. The second most common purpose is related to the job and the third is shopping and errands. Based on the description of the trip purpose, current evaluations do not observe a generalized role as a feeder solution for public transport.▪ Until now, this mobility service is not enough consolidated as an everyday transport solution since most of riders use the service with a monthly frequency or even less.▪ These results are coherent: leisure trips are occasional and more frequent during the afternoon/evening and weekends.▪ The main displaced mode is walking, around 40% of cases. In American cities, car trips also reaches similar substitution degree. However, in European cities, public transport is the second mode more affected by the arrival of scooters.▪ However, taking into account the proportion of scooter trips in the global mobility, its impact is limited.Environmental impact▪ Although scooters are introduced as a sustainable transport solution from an environmental perspective, several studies emphasize the current limitations that these services present today: short lifetimes, low daily usage rates and kilometers traveled by auxiliary vehicles for collection and distribution tasks among others. The first two are associated to a high impact for materials and manufacturing; the last one is connected to the day-to-day operation.▪ The estimations of their impacts show worse results than the rest of transport modes, only surpassed by cars. For that reason, the current mode substitution does not improve the sustainability of the transport system since the proportion of eco-friendly alliance (walking, public transport and cycling) is greater than the car displacement, for European cities more than for American ones.▪ To become a mode that improves the sustainability of the transport system, shared e-scooter services should achieve certain goals: lifetimes of 12-24 months, more than 10 kilometers traveled per scooter and day, fuel-efficient auxiliary vehicles, renewable energy sources, strategies to reduce the distance traveled due to operating tasks, and focused on the substitution of car trips.Infrastructure and urban space▪ Uncontrolled spread of scooters in cities has increased the pressure on transport infrastructure and urban space, creating conflicts with other vehicles and activities. The main frictions are the obstructions due to inappropriate parked scooters and unsafe riding on sidewalks.▪ However, the most common infrastructure where users ride is bike lanes, otherwise traffic lanes are the main alternative, being sidewalks the last option. Although riders would like to increase the use of segregated lanes for micromobility showing a lack of this type of infrastructure, or at least calming traffic streets.▪ In the same line, most of scooter are properly parked on sidewalks (corrals or furniture areas without obstructing other flows). However, the improperly parking takes long times up to some hours, an extra factor that explains the negative perception about these new mobility services. This seems a visual or aesthetic impact more than a real obstruction issue.Safety▪ Medical reports evidence a growth in the number of accidents where e-scooters are involved; although most of these incidents cause minor injuries, there are a certain percentage that require hospitalization and operations, even fatalities have been reported.▪ The most common accident only involves the same scooter (falls, infrastructure in bad conditions, collision with objects, vehicle malfunction). However, crashes with motorized vehicles are the accidents with severe consequences.▪ Accident rate estimated in different cities ranges from 20 to 70 accidents per 100,000 trips.▪ Riders using a helmet are a minority, around 10% or less, even in those cities where it is mandatory.▪ Since e-scooter trips are short, the perception of risk is smaller and users accept more risky behaviors.Measures and Policies▪ From a legislative perspective, assimilation of the e-scooter as a pre-existing vehicle either bicycle or motorized vehicle.▪ Cities order the uncontrolled and chaotic implementation of these services by means of constraints on the number of operators and fleet sizes. The former moves the competition off the road since companies should compete for operating permissions through a selection process. The latter meets the number of devices to the level of demand, introducing dynamic balancing depending on the usage rate of the e-scooters.▪ Different fees are introduced in order to compensate some of the externalities generated by shared e/scooter services. Additionally, several fines for operators and users try to encourage a better management, safer riding and properly parking.▪ Definition of non-riding (pedestrian streets, sidewalks), non-parking zones (parks, campus) and speed limits (10-30 km/h) in order to avoid conflicts with other transport modes and urban activities. Implementation of geofencing technology and speed controllers and lock-to technology in the devices to manage these measures.▪ Campaigns of education and communication promoted by cities and companies.▪ Equity policies to remove barriers that limit the accessibility to shared e-scooters: pricing discount programs, lack of smart technology for managing subscriptions, location of devices in areas of disadvantaged communities, vehicle design to avoid standing riding, etc.▪ Development of Mobility platforms to integrated the whole fleet of shared e-scooters in only one app, and extension to other transport modes to promote the role of feeder solution for public transport.▪ Systematic evaluation for the monitoring of the services, requiring collaboration from companies sharing their mobility data with cities.Based on the current situation of shared e-scooter services, there are still a need of knowledge at three different levels of analysis: understanding the role of this type of mobility solutions in the global transport system, guidelines and strategies for a competitive service design and operating measures for an efficient management of the day-to-day deployment.
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| 7. |
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| 8. |
- Johari, M., et al.
(författare)
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Effects of Near-Side and Far-Side Bus Stops on NMFD of Bi-Modal Urban Network
- 2019
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Ingår i: 2019 IEEE Intelligent Transportation Systems Conference, ITSC 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538670248 ; , s. 746-751
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Konferensbidrag (refereegranskat)abstract
- Recent studies through simulation and empirical data have shown that a Network Macroscopic Fundamental Diagram (NMFD or MFD) exists for multi-modal urban networks. However, more investigation should be conducted to explore the properties of multi-modal NMFD. In particular, the effects of operational characteristics of public transit like the number of lines, bus stop type, and bus stop location on multi-modal NMFD needs to be discussed. This paper discusses the effects of the near-side bus stop (those located before the intersection) and far-side bus stop (i.e. located after the intersection) on the NMFD of a bi-modal urban network in which cars and buses share the same space, i.e. there is no dedicated lane for buses. Results show that the NMFD in case of having far-side bus stops leads to a bigger range of critical density (density corresponded to maximum flow) for the car, while network capacity is almost the same. This results in a bigger optimal operational regime. Our findings, which are consistent with previous studies, yield that the far-side bus stop is superior to the near-side bus stop from the network operation perspective.
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| 9. |
- Leurent, F., et al.
(författare)
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Structural design of a hierarchical urban transit network integrating modal choice and environmental impacts
- 2019
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Ingår i: 21st EURO Working Group on Transportation Meeting, EWGT 2018, 17th – 19th September 2018, Braunschweig, Germany. - : Elsevier. ; , s. 99-106
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Konferensbidrag (refereegranskat)abstract
- The paper develops a structural model and a design methodology for transit system planning in an urban area. Transit "components" are modelled by subarea and by sub-mode in terms of line length, station spacing, and fleet size, in order to determine both quality of service and production costs. Roadway networks are modeled with a Macroscopic Fundamental Diagram that relates speed to network capacity and vehicle demand. Local and global environmental impacts are considered. Travel demand includes both mode-dependent users and mode-choosers able to adopt the mode that offers higher utility. The design methodology involves a mathematical program of welfare optimization with respect to transit factors and fares. Two definitions of welfare are given, one that takes into account only demand surplus and supply profit, the other including environmental impacts. An example of application to Greater Paris shows that there is room for system optimization under current subsidy conditions, and that the explicit inclusion of environmental impacts brings about a significant shift in the "optimal" policy package.
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| 10. |
- Poinsignon, François, et al.
(författare)
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Autonomous vehicle fleets for public transport : scenarios and comparisons
- 2022
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Ingår i: Green Energy and Intelligent Transportation. - : Elsevier BV. - 2773-1537 .- 2097-2512. ; 1:3
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Tidskriftsartikel (refereegranskat)abstract
- Autonomous vehicles (AVs) are becoming a reality and may integrate with existing public transport systems to enable the new generation of autonomous public transport. It is vital to understand what are the alternatives for AV integration from different angles such as costs, emissions, and transport performance. With the aim to support AV integration in public transport, this paper takes a typical European city as a case study for analyzing the impacts of different AV integration alternatives. A transport planning model considering AVs is developed and implemented, with a methodology to estimate the costs of the transport network. Traffic simulations are conducted to derive key variables related to AVs. An optimization process is introduced for identifying the optimal network configuration based on a given AV integration strategy, followed by the design of different AV integration scenarios, simulation, and analyses. With the proposed method, a case study is done for the city of Uppsala with presentation of detailed cost results together with key traffic statistics such as mode share. The results show that integrating AVs into public transport does not necessarily improve the overall cost efficiency. Based on the results and considering the long transition period to fully autonomous vehicles, it is recommended that public transport should consider a gradual introduction of AVs with more detailed analysis on different combination and integration alternatives of bus services and AVs.
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| 11. |
- Zhang, Wei, et al.
(författare)
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Efficiency of connected semi-autonomous platooning bus services in high-demand transit corridors
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The paper investigates the efficiency of serving high demand transit corridors with connected semi-autonomous busplatoons in both bus and BRT services. Platooning could make it possible to provide higher capacity than with conventionalbuses by forming virtual long buses out of multiple smaller vehicles, which could be particularly relevant inscenarios with large variation in demand between peak and off-peak hours. The problem is formulated as a constrainedoptimization problem to minimize total system cost, which includes waiting cost, access cost, riding cost, operatingcost and capital cost. For single period with fixed demand, both analytical solutions and numerical examples areprovided. Sensitivity analysis is carried out with regard to demand levels and capacity upper bound. The problemis generalized to a two-period problem considering peak and off-peak demand. Numerical results are provided withsensitivity analysis regarding average demand level and ratio of peak/off-peak demand. Furthermore, the impact of alower bound on service headway is investigated. The result shows that semi-autonomous vehicle platooning is competitivein medium and high demand scenarios, with the potential of reduced users’ cost and operator’s operating costat the expense of additional rolling stock cost. The minimum headway, restricted vehicle size, and higher demandratio all make semi-autonomous platooning more advantageous.
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| 12. |
- Zhang, Wei, et al.
(författare)
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Efficiency of Connected Semi-Autonomous Platooning Bus Services in High-Demand Transit Corridors
- 2022
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Ingår i: IEEE Open Journal of Intelligent Transportation Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2687-7813. ; 3, s. 435-448
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Tidskriftsartikel (refereegranskat)abstract
- The paper investigates the efficiency of serving high demand transit corridors with connected semi-autonomous bus platoons in both bus and BRT services. Platooning facilitates higher capacity than conventional buses by forming virtual long buses out of multiple smaller vehicles, which may be particularly relevant in scenarios with large demand variations between peak and off-peak hours. The problem is formulated as a constrained optimization problem to minimize total system cost, which includes waiting cost, access cost, riding cost, operating cost and capital cost. For a single period with fixed demand, both analytical solutions and numerical examples are provided. Sensitivity analysis is carried out with regard to demand levels and capacity upper bound. The problem is generalized to a two-period problem considering peak and off-peak demand. Numerical results are provided with sensitivity analysis regarding demand level and ratio of peak/off-peak demand. Furthermore, the impact of a lower bound on service headway is investigated. The result shows that semi-autonomous vehicle platooning is competitive in medium and high-demand scenarios, with the potential of reduced user costs and operating costs at the expense of additional rolling stock costs. Minimum headway constraint, restricted vehicle size, and higher demand ratio all make semi-autonomous platooning more advantageous.
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| 13. |
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| 14. |
- Zhang, Wei, et al.
(författare)
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Efficiency of semi-autonomous and fully autonomous bus services in trunk-and-branches networks
- 2019
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Ingår i: Journal of Advanced Transportation. - : Hindawi Publishing Corporation. - 0197-6729 .- 2042-3195.
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Tidskriftsartikel (refereegranskat)abstract
- Automation technology is expected to change the public transport sector radically in the future. One rising issue is whether to embrace the intermediate stage of semi-autonomous buses or to wait until fully autonomous buses are available. This paper proposes a cost model of bus operations considering automation technology. The generalized cost, which is the sum of waiting, riding, operating, and capital cost, is modeled for conventional, semi-autonomous, and fully autonomous bus services on a generic trunk-and-branches network. Semi-autonomous buses achieve reduced unit operating cost through automated platooning on the corridor. The relative efficiency of the different services is studied under a range of scenarios for commercial speed, network structure, and demand distribution. Analytical and numerical results show that fully autonomous buses exhibit great potential through reduced operating and waiting costs even if the additional capital cost is high. The advantages of semi-autonomous buses are weaker and most prominent in networks with low demand along a long corridor such as interurban networks. For both automation levels a commercial speed comparable to conventional vehicles is crucial. The established criteria provide input to planners and operators for understanding the potential of automated bus services.
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| 15. |
- Zhang, Wei
(författare)
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Planning and evaluation of autonomous vehicles in freight and public transport services
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The introduction of automation technology in transport systems brings both opportunities and challenges. The direct benefits of automation technology are obvious, for instance, reduced marginal driving cost, improved energy efficiency and increased safety. However, factors such as additional vehicle acquisition cost might hinder the implementation of autonomous vehicles, especially in the early stages when mass production is not realized yet. Besides, some benefits require large-scale applications or cooperation among multiple vehicles, while the low market penetration rate of autonomous vehicles may make system-specific benefits insignificant. Without proper planning and operation schemes, the advantages of automation technology can be cancelled out by its disadvantages. Given that the advantages of individual autonomous vehicles have been extensively explored, it is necessary to estimate the efficiency of transport systems involving autonomous vehicles. This thesis intends to solve the operation problem of autonomous vehicles in freight and public transport systems, focusing on system cost analysis.In freight transport, semi-autonomous truck platooning is a promising way to reduce fuel consumption. By instructing vehicles to form groups and drive together closely, the trailing vehicles experience reduced air resistance from the leading vehicle, and thus less fuel consumption. However, in practice, freight transport companies should also take time windows and transport reliability into consideration. The study answers the questions whether platoons should be formed and how significant can the savings be, considering driving cost, predefined time windows, travel time uncertainty and fuel cost. System optimization techniques, including stochastic optimization and mixed-integer linear programming, are adopted to minimize the total cost.In public transport, autonomous buses are assumed to save on-board crew cost, partially or fully. Similar with truck platoons, semi-autonomous buses can also form bus platoons for the purpose of eliminating the drivers from trailing buses. By contrast, fully autonomous buses are completely driverless and operates individually like conventional buses. To investigate the efficiency of autonomous buses, we compare the total cost of autonomous buses with conventional buses, where both passengers’ cost and service provider’s cost are modelled. In a general trunk-and-branches network connecting city center and suburbs, both fully autonomous bus and semi-autonomous bus systems are assessed. On a simple highly demanded corridor where demand varies during peak and off-peak hours, semi-autonomous bus platoons can be used as trains by extending its capacity in peak hours. Application of semi-autonomous vehicles are considered in traditional bus transit and BRT, by comparing with its conventional opponents.
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