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Transitioning towards the deployment of line-based autonomous buses: Consequences for service frequency and vehicle capacity
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.ORCID iD: 0000-0001-9447-2823
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.ORCID iD: 0000-0002-4506-0459
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.ORCID iD: 0000-0002-4106-3126
2020 (English)In: Transportation Research Part A: Policy and Practice, ISSN 0965-8564, E-ISSN 1879-2375, Vol. 138, p. 491-507Article in journal (Refereed) Published
Abstract [en]

The deployment of autonomous buses (AB) is expected to have consequences for service design facilitated by its cost function structure. We study the impacts of AB deployment in line-based public transport (PT) systems. In particular, we examine the transition phase where AB is sequentially deployed, involving the selection of lines for which AB will be introduced. To this end, we develop a modeling framework using a dynamic public transportation assignment and operations simulation model that captures users' adaptive path choices. An analytical model is used to determine the initial solutions in terms of service frequency and vehicle capacity for the simulation framework. Due to their different cost function structures, the deployment of AB may be accompanied by changes in the service frequency and vehicle capacity settings and consequently also on passenger flow distribution across the network. Both the simultaneous and the sequential deployment of AB on multiple lines are investigated. Deployment solutions are assessed in terms of the both total operator and user cost. The decision variables are vehicle capacity per line, service frequency per line and vehicle technology per line - i.e. either manually driven or fully automated buses. The framework is applied to a case study in Kista, Stockholm. The study shows that AB service have the potential to attract passengers through improved service provision. A sensitivity analysis is carried out concerning the effects of different cost parameters and demand levels on the deployment of AB in fixed line operations.

Place, publisher, year, edition, pages
Elsevier BV , 2020. Vol. 138, p. 491-507
National Category
Transport Systems and Logistics
Identifiers
URN: urn:nbn:se:kth:diva-272001DOI: 10.1016/j.tra.2020.06.019ISI: 000553351200029Scopus ID: 2-s2.0-85087711282OAI: oai:DiVA.org:kth-272001DiVA, id: diva2:1423595
Note

QC 20200909

Available from: 2020-04-15 Created: 2020-04-15 Last updated: 2022-06-26Bibliographically approved
In thesis
1. Transition Towards Fixed-Line Autonomous Bus Transportation Systems
Open this publication in new window or tab >>Transition Towards Fixed-Line Autonomous Bus Transportation Systems
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In the last years the steady development of autonomous driving technology has enabled the deployment of more mature autonomous vehicles. These vehicles have been applied in several pilot projects worldwide, most commonly in the form of small buses. At the same time, the amount of people traveling in especially urban areas is continuously growing, resulting in more trips in the transportation system. An efficient transportation system is therefore required to serve the growing passenger demand. Autonomous buses (AB) are assumed to have lower operational costs and with that public transport (PT) systems can potentially be designed more efficiently to facilitate the increased demand better. In this study, an AB specific simulation-based optimization framework is proposed which allows analyzing the impacts AB have on line-based PT systems. The thesis focuses on the transition from existing PT systems towards line-based PT systems operated partially or exclusively by AB.

Existing work on PT service design is extended so that realistic AB systems can be investigated. This is achieved by (i) using AB specific operator cost formulations, (ii) integrating infrastructure costs required for AB operations, (iii) utilizing a dynamic, stochastic and schedule-based passenger assignment model for the simulation of PT networks and by (iv) formulating a multi-objective optimization problem allowing to investigate the stakeholder-specific impacts of AB.

In Paper I the effects of AB, concerning service frequency and vehicle capacity, on fixed-line PT networks are investigated. Among other metrics, the changes are evaluated based on differences in level of service and passenger flow. Additionally, the sequential introduction of AB in existing PT systems is studied. The framework addresses a case study in Kista, Sweden. The study confirmed the initial hypothesis that the deployment of AB leads to an increase in service frequency and a marginal reduction in vehicle capacity. Furthermore, it could be seen that the deployment of AB increases the passenger load on AB lines and that passengers can shift from other PT modes towards the AB services.

Paper II incorporates a multi-objective heuristic optimization algorithm in the simulation framework. The study investigates changes in transport network design based on the deployment of AB. The differences in user-focused and operator-focused network design are analyzed and the impact of AB on these is quantified. This study is applied to a case study in Barkarby, Sweden where a full-sized, line-based PT network is designed to exclusively operate AB. Among other findings, we show that the autonomous technology reduces the number of served bus stops and reduces the total PT network size. Additionally, average passenger waiting time can be reduced when deploying AB on user-focused PT networks, which in turn leads to a further reduction of user cost.

Abstract [sv]

De senaste årens framsteg inom autonom körteknik har lett till mer mogna autonoma fordon. Dessa fordon har setts tillämpas i flera pilotprojekt över hela världen, oftast i form av små bussar. Samtidigt växer mängden människor som reser, särskilt i stadsområden, kontinuerligt vilket resulterar i fler resor i transportsystemet. Därför krävs ett effektivt transportsystem för att tillgodose det växande antalet passagerare. Autonoma bussar (AB) antas ha lägre driftskostnader och därmed kan system för kollektivtrafik (public transport, PT) potentiellt utformas mer effektivt för att underlätta den ökade efterfrågan bättre. I denna studie föreslås ett AB-specifikt simuleringsbaserat optimeringsramverk som gör det möjligt att analysera effekterna AB har på linjebaserade PT-system. Avhandlingen fokuserar på övergången från befintliga PT-system till linjebaserade PT-system som delvis eller uteslutande drivs av AB.

Befintligt arbete med PT-tjänstdesign utvidgas så att realistiska AB-system kan undersökas. Detta uppnås genom att (i) använda AB-specifika operatörskostnadsformuleringar, (ii) integrera infrastrukturkostnader som krävs för AB-verksamhet, (iii) använda en dynamisk, stokastisk och schemabaserad modell för att tilldela passagerare vid simulering av PT-nät samt genom att (iv) formulera ett multifunktionellt optimeringsproblem som gör det möjligt att undersöka AB: s intressespecifika effekter.

I artikel I undersöks effekterna av AB, med avseende på servicefrekvens och fordonskapacitet, på fasta linjer i PT-nät. Förändringar utvärderas bland annat utifrån skillnader i servicenivå och passagerarflöde. Dessutom studeras den sekventiella introduktionen av AB i befintliga PT-system. Det föreslagna ramverket tillämpas på en fallstudie i Kista, Sverige. Studien bekräftade den initiala hypotesen att utplaceringen av AB leder till en ökning av servicefrekvensen och en marginell minskning av fordonens kapacitet. Vidare kunde man se att utplaceringen av AB ökar passagerarbelastningen på AB-linjer och att passagerare kan skifta från andra PT-former mot AB-tjänsterna.

Artikel II integrerar en multifunktionell heuristisk optimeringsalgoritm i ramverket för simuleringen. Studien undersöker förändringar i transportnätverkets design baserat på implementeringen av AB. Skillnaderna i användarfokuserad och operatörsfokuserad nätverksdesign analyseras och AB: s inverkan på dessa kvantifieras. Denna studie tillämpas på en fallstudie i Barkarby, Sverige, där ett fullstort linjebaserat PT-nät är utformat för att exklusivt driva AB. Vi visar bland annat att den autonoma tekniken reducerar antalet använda busshållplatser och reducerar den totala PT-nätstorleken. Dessutom kan implementeringen av AB på användarfokuserade PT-nät ytterligare förbättra servicenivån främst genom att minska den genomsnittliga väntetiden per passagerare.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. p. 23
Series
TRITA-ABE-DLT ; 2011
Keywords
Autonomous Buses, Public Transportation, Network Design, Resource Allocation, Simulation-based multi-objective Optimization
National Category
Transport Systems and Logistics
Research subject
Transport Science
Identifiers
urn:nbn:se:kth:diva-272008 (URN)978-91-7873-514-3 (ISBN)
Presentation
2020-05-25, https://kth-se.zoom.us/j/543209993, Du som saknar dator/datorvana kan kontakta jenelius@kth.se för information"., 10:00 (English)
Opponent
Supervisors
Available from: 2020-04-29 Created: 2020-04-15 Last updated: 2022-06-26Bibliographically approved
2. Simulation and optimization of innovative urban transportation systems
Open this publication in new window or tab >>Simulation and optimization of innovative urban transportation systems
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The ongoing trends of urbanization and e-commerce continuously challenge the existing urban transportation systems. A steadily growing number of people traveling within urban areas, results in more trips taken with public transportation systems. Additionally, the constantly increasing number of urban logistic operations leads to more commercial vehicles in cities. These ongoing trends and the need for more sustainable operations require the design of robust and efficient transportation systems which additionally provide a high level of service for their users. In recent years, two innovative approaches have been proposed to overcome these challenges. That is, first, the use of autonomous buses as a replacement, or an addition to existing public transportation systems, and second, the consideration of consolidating multiple types of demand (i.e. passenger and freight) when planning and designing transportation systems. In this thesis, both approaches are studied and their impact on urban transportation systems is evaluated. This is achieved by developing novel simulation-based optimization models that consider technology-specific cost structures and capture the changed mode of operation for different vehicle technologies.

In Papers I and II the deployment of autonomous buses on fixed-line public transportation networks is investigated. Changes in service frequency, vehicle capacity, and metrics corresponding to the level of service for public transportation users due to new vehicle technology are investigated. Furthermore, Paper I explores the transition from conventional public transportation systems to systems operated by autonomous buses, while Paper II investigates the changes in network design due to autonomous bus operations. The developed models are applied to case studies in Kista, Sweden, and Barkarby, Sweden. Two key results can be identified in these studies. First, autonomous bus deployment leads to an increase in service frequency, while waiting time for passengers can be reduced. Second, more passengers are attracted to autonomous bus lines by reducing the access walking distances and increased level-of-service. On more complex networks these trends are amplified. 

In each of Papers III and IV, a novel pickup and delivery model is proposed. The models consider vehicle concepts which allow for the consolidated transport of multiple demand types. In Paper III the vehicles can serve different types of demand by exchanging purpose-specific modules at dedicated service depots, while in Paper IV individual demand-specific vehicles can form platoons with modular length and varying configuration. The results of the extensive scenario studies and parameter analysis show that for multi-purpose vehicle operations (Paper III) the total costs can be reduced by an average of 13% and for platoon operations (Paper IV) the total costs are reduced by over 48%. In both models, the cost savings stem mainly from a reduction in fleet size, total vehicle trip duration, and the total distance traveled.

Abstract [sv]

De pågående trenderna med urbanisering och e-handel utmanar kontinuerligt de befintliga stadstransportsystemen. Ett stadigt växande antal människor som reser inom tätorter leder till fler resor med kollektivtrafik (PT). Dessutom leder det ständigt ökande antalet urbana logistikverksamheter till fler kommersiella fordon i städerna. Dessa pågående trender och behovet av mer hållbar verksamhet kräver design av robusta och effektiva transportsystem som dessutom ger en hög servicenivå för sina användare. Under de senaste åren har två innovativa tillvägagångssätt föreslagits för att övervinna dessa utmaningar. Det vill säga, för det första, användningen av autonoma bussar (AB) som en ersättning, eller ett tillägg till befintliga PT-system, och för det andra, övervägandet av att konsolidera flera typer av efterfrågan (dvs. passagerare och gods) vid planering och utformning av transportsystem. I denna avhandling studeras båda tillvägagångssätten och deras inverkan på stadstransportsystem utvärderas. Detta uppnås genom att utveckla nya simuleringsbaserade optimeringsmodeller som tar hänsyn till teknikspecifika kostnadsstrukturer och fångar det förändrade driftsättet för olika fordonsteknologier.

I Paper I och II undersöks utbyggnaden av AB på fasta PT-nät. Förändringar i servicefrekvens, fordonskapacitet och mått som motsvarar servicenivån för PT-användare på grund av ny fordonsteknik undersöks. Vidare undersöker Paper I den sekventiella  övergången från konventionella PT-system till system som drivs av AB, medan Paper II undersöker förändringarna i nätverksdesign på grund av AB-drift. De utvecklade modellerna tillämpas på fallstudier i Kista, Sverige och Barkarby, Sverige. Två nyckelresultat kan identifieras i dessa studier. För det första leder AB-insatsen till en ökad servicefrekvens, samtidigt som väntetiden för passagerarna kan minskas. För det andra lockas fler passagerare till linjer med AB genom att gångavstånden minskas och servicenivån ökas. På mer komplexa nätverk förstärks dessa trender.

I vart och ett av dokumenten III och IV föreslås en ny modell för hämtning och leverans. Modellerna tar hänsyn till fordonskoncept som möjliggör konsoliderad transport för olika typer av efterfrågan. I Paper III kan fordonen betjäna olika typer av efterfrågan genom att byta ut ändamålsspecifika moduler på dedikerade servicedepåer, medan i Paper IV kan individuella behovsspecifika fordon bilda plutoner med modullängd och varierande konfiguration. Resultaten av de omfattande scenariestudierna och parameteranalysen visar att för multi-purpose vehicle operations (Paper III) kan de totala kostnaderna minskas med i genomsnitt 13% och för pluton operationer (Paper IV) de totala kostnaderna minskas med över 48%. I båda modellerna härrör kostnadsbesparingarna huvudsakligen från en minskning av flottans storlek, totala fordonsresan och den totala tillryggalagda sträckan.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2022. p. 46
Series
TRITA-ABE-DLT ; 2225
National Category
Transport Systems and Logistics
Research subject
Transport Science, Transport Systems
Identifiers
urn:nbn:se:kth:diva-311840 (URN)978-91-8040-256-9 (ISBN)
Public defence
2022-06-14, Kollegiesalen, Brinellvägen 8, KTH Campus, videolänk https://kth-se.zoom.us/j/65778805858, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20220518

Available from: 2022-05-18 Created: 2022-05-16 Last updated: 2022-06-25Bibliographically approved

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