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Häll, C. H., Ceder, A. (., Ekström, J. & Quttineh, N.-H. (2018). Adjustments of public transit operations planning process for the use of electric buses. Journal of Intelligent Transportation Systems / Taylor & Francis, 1-15
Open this publication in new window or tab >>Adjustments of public transit operations planning process for the use of electric buses
2018 (English)In: Journal of Intelligent Transportation Systems / Taylor & Francis, ISSN 1547-2450, E-ISSN 1547-2442, p. 1-15Article in journal (Refereed) Epub ahead of print
Abstract [en]

This work investigates and discusses how the introduction of electric buses (EB), both battery and plug-in hybrid EB, will and should change the operations planning of a public transit system. It is shown that some changes are required in the design of a transit route network, and in the timetabling and vehicle scheduling processes. Other changes are not required, but are advisable, using this opportunity upon the introduction of EB. The work covers the main characteristics of different types of EB with a short description, including the most popular charging technologies, and it presents the generally accepted transit operations planning process. Likewise, it describes and analytically formulates new challenges that arise when introducing EB. The outcome of the analyses shows that multiple new considerations must take place. It is also shown that the different charging techniques will influence the operations planning process in different ways and to a varying extent. With overnight, quick and continuous charging, the main challenges are in the network route design step, given the possibility of altering the existing network of routes, with efficient and optimal changes of the timetabling and vehicle scheduling components. An illustrative example, based on four bus lines in Norrköping, Sweden, is formulized and introduced using three problem instances of 48, 82, and 116 bus trips. The main results exhibit the minimum number of vehicles required using different scenarios of charging stations.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-152547 (URN)10.1080/15472450.2018.1488131 (DOI)
Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06
Ekström, J. (2018). Comparison of usage-based congestion pricing schemes. In: Proceedings Transportation Research Board 97th Annual Meeting: . Paper presented at Transportation Research Board 97th Annual Meeting, January 7-11, 2018 in Washington, D.C, USA. Washington D.C.
Open this publication in new window or tab >>Comparison of usage-based congestion pricing schemes
2018 (English)In: Proceedings Transportation Research Board 97th Annual Meeting, Washington D.C., 2018Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates how usage-based pricing can be applied in order to improve the efficiency of the transportation system. Distance-based, travel time-based and delayed-based pricing schemes are investigated, both from a one-link and network perspective. A static modeling framework is adopted, based on user-equilibrium, and a simplified emission model based on the HBEFA emission model is used. Optimal usage-based fees are calculated using a surrogate-based optimization framework, and determination of zone layout is done using k-means clustering. The results for a Stockholm region network show that already with network wide pricing a large proportion of the maximum improvement of social surplus achievable with first-best pricing, can be reached. Delay-based pricing, in which the users are charged based on the excess travel time in comparison to free flow travel times, achieves 99% of the maximum improvement, already with one single fee across the whole network. With clustering of links based on their first-best optimal fees, the benefits of both distance and travel time-based fees can significantly be improved.

Place, publisher, year, edition, pages
Washington D.C.: , 2018
Series
TRB Annual Meeting Online
National Category
Engineering and Technology Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-147982 (URN)
Conference
Transportation Research Board 97th Annual Meeting, January 7-11, 2018 in Washington, D.C, USA
Funder
Swedish Energy Agency, 38921-1
Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-06-13
Quttineh, N.-H., Häll, C. H., Ekström, J. & Ceder, A. (2017). Combined Timetabling and Vehicle Scheduling for Electric Buses. In: Proceedings of the 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, 2017, Hong Kong, China: . Paper presented at The 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, Hong Kong, China. Hong Kong: HKSTS
Open this publication in new window or tab >>Combined Timetabling and Vehicle Scheduling for Electric Buses
2017 (English)In: Proceedings of the 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, 2017, Hong Kong, China, Hong Kong: HKSTS , 2017, , p. 8Conference paper, Oral presentation only (Other academic)
Abstract [en]

In this paper we present a novel mathematical model, integrating the timetabling and vehicle schedulingproblems for electric buses. The objective is to minimize the number of buses while satisfying constraintsconcerning routing and charging, including design choices of where to install charging equipment. Weillustrate the different effects of tackling the timetabling and vehicle scheduling of electric buses as separateproblems or as a joint problem, both for fixed and variable headways. To do so, tests are performed with: (i) given timetable, i.e. solving only the vehicle scheduling problem, (ii) fixed headways for each line, (iii) variable headways. For these tests, a small case based on four bidirectional bus lines is used.

Place, publisher, year, edition, pages
Hong Kong: HKSTS, 2017. p. 8
Keywords
Electric Buses, Transit Operations Planning, Timetabling, Vehicle Scheduling, MIP modeling
National Category
Computational Mathematics Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-148490 (URN)
Conference
The 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, Hong Kong, China
Funder
Swedish Energy Agency, 40377-1
Available from: 2018-06-12 Created: 2018-06-12 Last updated: 2018-08-30Bibliographically approved
Tsanakas, N., Ekström, J. & Olstam, J. (2017). Emission estimation based on cross-sectional traffic data. In: Prceedings of the 22nd International Transportation and Air Pollution Conference: . Paper presented at 22nd International Transportation and Air Pollution Conference, Zürich, Switzerland, 15-16 November 2017.
Open this publication in new window or tab >>Emission estimation based on cross-sectional traffic data
2017 (English)In: Prceedings of the 22nd International Transportation and Air Pollution Conference, 2017Conference paper, Published paper (Refereed)
National Category
Civil Engineering Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-147873 (URN)
Conference
22nd International Transportation and Air Pollution Conference, Zürich, Switzerland, 15-16 November 2017
Projects
Förbättrad prognos av energianvändning och emissioner vid styrmedelsanalys i vägtrafiken
Funder
Swedish Energy Agency, 38921-1
Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2018-05-30Bibliographically approved
Allström, A., Ekström, J., Gundlegård, D., Ringdahl, R., Rydergren, C., Bayen, A. M. & Patire, A. D. (2016). A hybrid approach for short-term traffic state and travel time prediction on highways. In: TRB 95th annual meeting compendium of papers: . Paper presented at Transportation Research Board 95th Annual Meeting, 2016-1-10 to 2016-1-14 Washington DC, United States.
Open this publication in new window or tab >>A hybrid approach for short-term traffic state and travel time prediction on highways
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2016 (English)In: TRB 95th annual meeting compendium of papers, 2016Conference paper, Published paper (Refereed)
Abstract [en]

Traffic management and traffic information are essential in urban areas, and require a good knowledge about both the current and the future traffic state. Both parametric and non-parametric traffic state prediction techniques have previously been developed, with different advantages and shortcomings. While non-parametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during non-recurring traffic conditions such as incidents and events. Hybrid approaches, combining the two prediction paradigms have previously been proposed by using non-parametric methods for predicting boundary conditions used in a parametric method. In this paper we instead combine parametric and non-parametric traffic state prediction techniques through assimilation in an Ensemble Kalman filter. As non-parametric prediction method a neural network method is adopted, and the parametric prediction is carried out using a cell transmission model with velocity as state. The results show that our hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 minutes into the future, using a prediction horizon of up to 50 minutes ahead in time to allow the journey to be completed.

National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-125386 (URN)
Conference
Transportation Research Board 95th Annual Meeting, 2016-1-10 to 2016-1-14 Washington DC, United States
Projects
Mobile Millenium Stockholm
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Available from: 2016-02-22 Created: 2016-02-22 Last updated: 2016-06-03
Allström, A., Ekström, J., Gundlegård, D., Ringdahl, R., Rydergren, C., Bayen, A. M. & Patire, A. D. (2016). Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways. Transportation Research Record, 2554, 60-68
Open this publication in new window or tab >>Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways
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2016 (English)In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2554, p. 60-68Article in journal (Refereed) Published
Abstract [en]

Traffic management and traffic information are essential in urban areas and require reliable knowledge about the current and future traffic state. Parametric and nonparametric traffic state prediction techniques have previously been developed with different advantages and shortcomings. While nonparametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during nonrecurring traffic conditions, such as incidents and events. Hybrid approaches have previously been proposed; these approaches combine the two prediction paradigms by using nonparametric methods for predicting boundary conditions used in a parametric method. In this paper, parametric and nonparametric traffic state prediction techniques are instead combined through assimilation in an ensemble Kalman filter. For nonparametric prediction, a neural network method is adopted; the parametric prediction is carried out with a cell transmission model with velocity as state. The results show that the hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 min into the future, with a prediction horizon of up to 50 min ahead in time to allow the journey to be completed

Place, publisher, year, edition, pages
Washington, DC, USA: The National Academies of Sciences, Engineering, and Medicine, 2016
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-132632 (URN)10.3141/2554-07 (DOI)000388911900008 ()
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

Funding agencies: Swedish Transport Administration

Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2017-11-29Bibliographically approved
Ekström, J., Kristoffersson, I. & Quttineh, N.-H. (2016). Surrogate-based optimization of cordon toll levels in congested traffic networks. Journal of Advanced Transportation, 50(6), 1008-1033
Open this publication in new window or tab >>Surrogate-based optimization of cordon toll levels in congested traffic networks
2016 (English)In: Journal of Advanced Transportation, ISSN 0197-6729, E-ISSN 2042-3195, Vol. 50, no 6, p. 1008-1033Article in journal (Refereed) Published
Abstract [en]

The benefits, in terms of social surplus, from introducing congestion pricing schemes in urban networks are depending on the design of the pricing scheme. The major part of the literature on optimal design of congestion pricing schemes is based on static traffic assignment, which is known for its deficiency in correctly predict travels in networks with severe congestion. Dynamic traffic assignment can better predict travel times in a road network, but are more computational expensive. Thus, previously developed methods for the static case cannot be applied straightforward. Surrogate-based optimization is commonly used for optimization problems with expensive-to-evaluate objective functions. In this paper we evaluate the performance of a surrogate-based optimization method, when the number of pricing schemes which we can afford to evaluate (due to the computational time) is limited to between 20 and 40. A static traffic assignment model of Stockholm is used for evaluating a large number of different configurations of the surrogatebased optimization method. Final evaluation is done with the dynamic traffic assignment tool VisumDUE, coupled with the demand model Regent, for a Stockholm network including 1 240 demand zones and 17 000 links. Our results show that the surrogate-based optimization method can indeed be used for designing a congestion pricing scheme which return a high social surplus.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2016
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-126894 (URN)10.1002/atr.1386 (DOI)000386040200005 ()
Available from: 2016-04-06 Created: 2016-04-06 Last updated: 2017-05-22Bibliographically approved
Hadera, H., Wide, P., Harjunkoski, I., Mäntysaari, J., Ekström, J., Sand, G. & Engell, S. (2015). A Mean Value Cross Decomposition Strategy for Demand-side Management of a Pulping Process. In: Krist V. Gernaey, Jakob K. Huusom and Gani Rafiqul (Ed.), 12th International Symposium on Process Systems Engineering and 25th European Symposium on Computer Aided Process Engineering: (pp. 1931-1936). Elsevier, 37
Open this publication in new window or tab >>A Mean Value Cross Decomposition Strategy for Demand-side Management of a Pulping Process
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2015 (English)In: 12th International Symposium on Process Systems Engineering and 25th European Symposium on Computer Aided Process Engineering / [ed] Krist V. Gernaey, Jakob K. Huusom and Gani Rafiqul, Elsevier , 2015, Vol. 37, p. 1931-1936Chapter in book (Refereed)
Abstract [en]

Energy is becoming a critical resource for process industries as introduction of new policies drive changes in the energy supply systems. Energy availability and pricing is much more volatile. In this study, we propose a Mean Value Cross Decomposition approach to functionally separate production scheduling from energy-cost optimization. Such a decomposition makes it possible to exploit existing optimization solutions avoiding a need to create a new monolithic model. The proposed framework is applied to a continuous process of thermo-mechanical pulping using a discrete-time Resource-Task Network model. Example case study scenarios show that the approach gives optimal system-wide solutions while keeping the models separated.

Place, publisher, year, edition, pages
Elsevier, 2015
Series
Computer Aided Chemical Engineering, ISSN 1570-7946 ; 37
Keywords
Scheduling, demand-side management, mean value cross decomposition
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:liu:diva-119621 (URN)10.1016/B978-0-444-63576-1.50016-9 (DOI)000366893400016 ()978-0-444-63429-0 (ISBN)
Available from: 2015-06-23 Created: 2015-06-23 Last updated: 2019-01-23Bibliographically approved
Ekström, J., Kristoffersson, I. & Quttineh, N.-H. (2015). Surrogatbaserad optimering av avgiftsnivåer i trängselavgiftssystem.
Open this publication in new window or tab >>Surrogatbaserad optimering av avgiftsnivåer i trängselavgiftssystem
2015 (Swedish)Report (Other academic)
Abstract [sv]

Trängselskatt finns idag i både Stockholm och Göteborg, och det är troligt att utformningen av dessa trängselskattesystem kommer att justeras framöver med avseende på avgiftsnivå, placering och tidpunkt. För Stockholm finns beslut om ändring från januari 2016 och i Göteborg ändrades avgiftsnivåerna i januari 2015. I detta projekt utvecklas metoder som ska kunna ge stöd vid justering av avigiftsnivåer, så att en så stor samhällsekonomisk nytta som är möjligt uppnås med trängselskattesystemet.

För storstadsområden, där det under rusningstrafik är trängsel i delar av nätverket, är trängselskatt främst intressant att analysera med dynamiska transportmodeller. Tidigare utveckling av metoder för optimal avgiftssättning har dock främst fokuserat på statiska modeller, exempelvis Emme, som har kända problem med att korrekt uppskatta förändring i restider när det är trängsel i delar av trafiknätverket. I detta projekt har vi därför tillämpat surrogat-baserad optimering, som är en metodansats som ställer få krav på vilken transportmodell som används. Den dynamiska transportmodellen Regent/VisumDUE finns sedan tidigare implementerad för Stockholmsregionen, och har därför även använts i detta projekt. VisumDUE är en makroskopisk nätutläggningsmodell med dynamiskt ruttval, och Regent är en efterfrågemodell som innehåller resgenerering, färdmedelsval och destinationsval för arbetsresor[1].

Surrogat-baserad optimering erbjuder ett ramverk för optimering av problem med beräkningsmässigt kostsamma målfunktioner. Genom att approximera en funktionsyta till samplade punkter från den kostsamma målfunktionen, kan optimeringen istället göras över den approximerade funktionsytan. För Regent/VisumDUE tar utvärderingen av ett givet trängselskattescenario ca tio timmar, och det är denna beräkningstid som gör målfunktionen kostsam. Givet ett antal samplade punkter, görs ytterligare sampling utifrån en given strategi för att förbättra approximationen, så kallad iterativ sampling. Inom ramverket finns dock en mängd möjligheter för hur de olika komponenterna designas. Därför är det svårt att utvärdera surrogat-baserad optimering med endast Regent/VisumDUE. En statisk transportmodell har därför använts för att utvärdera ett antal kombinationer av samplingsstrategi och funktionsyta. Den mest lovande kombinationen har sedan även utvärderats med Regent/VisumDUE. För att vara praktiskt tillämpbart i framtiden har fokus i projektet varit att utvärdera hur metodansatsen fungerar när antalet möjliga tulluppsättningar är kraftigt begränsat (20-40 stycken).

Det scenario som har använts som grund i projektet är trängselskatt i Stockholm på nuvarande tullring, på Essingeleden samt på innerstadsbroarna. Skatten är differentierad med avseende på riktning, vilket ger sex olika skattenivåer att optimera. Optimeringen har gjorts för trängselskattenivå under maxtimmen. I det dynamiska fallet har trängselskattens nivå utanför maxtimme funnits med som indata, men samma tidsprofil som på nuvarande tullring har antagits i alla scenarier (avgiftstrappa 50%, 75%, 100%, 75%, 50%). Utvärderingen med den statiska transportmodellen visar att lösningar nära globalt optimum kan uppnås med endast 40 utvärderade trängselskattenivåer, och en tydlig förbättring av den samhällsekonomiska nyttan uppnås redan vid 20 utvärderade trängselskattenivåer.

Även med ett kraftigt begränsat antal utvärderingar av den kostsamma målfunktionen i Regent/VisumDUE, har vi visat att det är möjligt att använda metodansatsen. En tydlig förbättring av den samhällsekonomiska nyttan uppnås med endast 22 utvärderade trängselskattenivåer. Ytterligare experiment skulle dock behövas för att undersöka hur stor denna förbättring är i förhållande till vad som skulle kunna uppnås.

Publisher
p. 25
Keywords
trängselskatt, trängselavgift, vägavgifter
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-121706 (URN)
Projects
Optimala vägavgifter med dynamiska modeller
Available from: 2015-10-02 Created: 2015-10-02 Last updated: 2015-10-07Bibliographically approved
Ekström, J. (2014). Finding second-best toll locations and levels by relaxing the set of first-best feasible toll vectors. European Journal of Transport and Infrastructure Research, 14(1), 7-29
Open this publication in new window or tab >>Finding second-best toll locations and levels by relaxing the set of first-best feasible toll vectors
2014 (English)In: European Journal of Transport and Infrastructure Research, ISSN 1567-7133, E-ISSN 1567-7141, Vol. 14, no 1, p. 7-29Article in journal (Refereed) Published
Abstract [en]

This paper provides a framework for optimizing toll locations and levels in congestion pricing schemes for large urban road networks, with the objective to maximize the social surplus. This optimization problem is referred to as the toll location and level setting problem (TLLP) and is both non-convex, non-smooth and involves binary decision variables, and is therefore considered as a hard problem to solve. In this paper a solution approach is provided which instead of directly solving the TLLP, makes use of the first-best toll level solution, in which no restrictions are imposed on toll locations or levels. A first-best pricing scheme can be obtained by solving a convex program, and it has previously been shown that for the used routes in the network, the first-best toll levels on a route level are unique. By formulating an optimization problem, which instead of maximizing the social surplus, tries to find the link toll levels which minimize the deviation from first-best route tolls, a mixed integer linear program is obtained, and if the toll locations are predetermined the resulting optimization problem is a linear program.

The approach of minimizing the deviation from first--best route tolls is applied for two different network models, and results are provided to show the applicability of the approach, as well as to compare with other approaches. Also, it is shown that for the Stockholm network, virtually the first-best level of social surplus can be obtained with a significantly reduced number of located tolls.

Place, publisher, year, edition, pages
Technische Universiteit Delft, 2014
Keywords
congestion pricing, network design, user equilibrium
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-104440 (URN)000331883900003 ()2-s2.0-84894064255 (Scopus ID)
Available from: 2014-02-17 Created: 2014-02-17 Last updated: 2017-12-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1367-6793

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