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Simulation and optimization of innovative urban transportation systems
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.ORCID iD: 0000-0001-9447-2823
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: urn:nbn:se:kth:diva-311840ISBN: 978-91-8040-256-9 (print)OAI: oai:DiVA.org:kth-311840DiVA, id: diva2:1658249
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
List of papers
1. Transitioning towards the deployment of line-based autonomous buses: Consequences for service frequency and vehicle capacity
Open this publication in new window or tab >>Transitioning towards the deployment of line-based autonomous buses: Consequences for service frequency and vehicle capacity
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
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-272001 (URN)10.1016/j.tra.2020.06.019 (DOI)000553351200029 ()2-s2.0-85087711282 (Scopus ID)
Note

QC 20200909

Available from: 2020-04-15 Created: 2020-04-15 Last updated: 2022-06-26Bibliographically approved
2. Network design for line-based autonomous bus services
Open this publication in new window or tab >>Network design for line-based autonomous bus services
2022 (English)In: Transportation, ISSN 0049-4488, E-ISSN 1572-9435, Vol. 49, no 2, p. 467-502Article in journal (Refereed) Published
Abstract [en]

The maturing of autonomous driving technology in recent years has led to several pilot projects and the initial integration of autonomous pods and buses into the public transport (PT) system. An emerging field of interest is the design of public transport networks operating autonomous buses and the potential to attract higher levels of travel demand. In this work a multi-objective optimization and multi-agent simulation framework is developed to study potential changes in the network design and frequency settings compared to conventional PT systems when autonomous vehicles (AV) systems are deployed on fixed-route networks. During the optimization process multiple deployment scenarios (network configurations and service frequency) are evaluated and optimized considering the operator cost, user cost and infrastructure preparation costs of the system. User-focused network design and operator-focused network design are studied for a real-world urban area in Sweden. The results provide insights into the network design and level of service implications brought about by the deployment of autonomous bus (AB) when those are integrated in route-based PT systems. We show that the deployment of autonomous buses result with a network design that increases service ridership. In the context of our case study this increase is likely to primarily substitute walking.

Place, publisher, year, edition, pages
Springer Nature, 2022
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-292901 (URN)10.1007/s11116-021-10183-7 (DOI)000628070400001 ()2-s2.0-85102500377 (Scopus ID)
Funder
Integrated Transport Research Lab (ITRL)Vinnova
Note

QC 20221025

Available from: 2021-04-15 Created: 2021-04-15 Last updated: 2023-10-09Bibliographically approved
3. Multi-purpose Pickup and Delivery Problem for Combined Passenger and Freight Transport
Open this publication in new window or tab >>Multi-purpose Pickup and Delivery Problem for Combined Passenger and Freight Transport
(English)In: Transportation Research Part E: Logistics and Transportation Review, ISSN 1366-5545, E-ISSN 1878-5794Article in journal (Refereed) Submitted
Abstract [en]

Recent developments in modular transport vehicles allow deploying multi-purpose vehicles which can alternately transport different kinds of flows. In this study, we propose a novel variant of the pickup and delivery problem, the multi-purpose pickup and delivery problem, where multi-purpose vehicles are assigned to serve a multi-commodity flow. We solve a series of use case scenarios using an exact optimization algorithm and an adaptive large neighborhood search algorithm. We compare the performance of a multi-purpose vehicle fleet to a mixed single-use vehicle fleet. Our findings suggest that total costs can be reduced by an average of 13% when multi-purpose vehicles are deployed, while at the same time reducing the total vehicle trip duration and total distance travelled by an average of 33% and 16%, respectively. The size of the fleet can be reduced by an average of 35%. The results can be used by practitioners and policymakers to decide on whether the combination of passenger and freight demand flows with multi-purpose vehicles in a given system will yield benefits compared to existing fleet configurations.

Keywords
Public transportation, Freight transportation, Modular vehicles, Heuristic optimization
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-311837 (URN)
Funder
Vinnova, 2020-00565Swedish National Infrastructure for Computing (SNIC), 2018-05973
Note

QCR 20220509

Available from: 2022-05-04 Created: 2022-05-04 Last updated: 2022-06-25Bibliographically approved
4. Modular Vehicle Routing for Combined Passenger and Freight Transport
Open this publication in new window or tab >>Modular Vehicle Routing for Combined Passenger and Freight Transport
(English)In: Article in journal (Refereed) Submitted
Abstract [en]

The continuous increase in urban deliveries and the ongoing urbanization of large cities require the development of efficient and sustainable transportation solutions. This study investigates the impact of modular vehicle concepts and the consolidation of different demand types in the route planning on the efficiency of the urban freight and passenger transportation system. Modularity is achieved by connecting multiple vehicles together to form a platoon. The consolidation of different demand types is realized by simultaneously consider passenger and freight demand in the optimization algorithm. The considered vehicles are specific for each demand type by can be connected freely, hence it is possible to transport different demand types in the same platoon. The cost terms in the problem formulation are comprised of travel time costs, travel distance costs, fleet size costs, and cost considering unserved requests. The modular vehicle operations are modeled in a novel pickup and delivery problem which is solved using CPLEX and Adaptive Large Neighborhood Search (ALNS). In an extensive scenario study, the potentials of the new modular vehicle type are explored for different spatial and temporal demand distributions. A parameter study on vehicle capacity, vehicle range and cost saving assumptions is performed to study their influence on the efficiency. The experiments carried out indicate a general cost savings of 48% due to modularity and an additional 9% due to consolidation. The reduction mainly stems from reduced operating costs and reduced trip duration, while the same number of requests can be served in all cases. Empty vehicle kilometers are reduced by more than 60% by consolidation and modularity. The proposed model and optimization framework can be used by companies and policy makers to identify required fleet sizes, optimal vehicle routes and cost savings due to different types of operation and vehicle technology.

Keywords
Public transportation, Freight transportation, Modular vehicles, Heuristic optimization
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-311839 (URN)
Funder
Vinnova, 2020-00565Swedish National Infrastructure for Computing (SNIC), 2018-05973
Note

QCR 20220509

Available from: 2022-05-04 Created: 2022-05-04 Last updated: 2022-06-25Bibliographically approved

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Hatzenbühler, Jonas

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