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Congestion Effects in Transport Modelling and Forecasting
KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. Sweco.ORCID iD: 0000-0003-3043-8145
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Transport investments and policies are increasingly turned towards dealing with transport congestion rather than with shortening the potential free flow travel time. However, appraisal methodologies for projects meant to reduce congestion are relatively less well developed compared to methodologies for projects aiming to reduce travel times. Static assignment models are for instance incapable of predicting the build-up and dissipation of traffic queues and capturing the experienced crowding caused by uneven on-board passenger loads. Despite of the availability of dynamic traffic assignment and despite of fairly concrete ideas of how integration with demand models could take place, only few model systems have been developed for real applications.

The predicted reduction of traffic volume across the Gothenburg congestion charge cordon in the peak, 11%, turned out to be an accurate estimate of the observed reduction, 12%. The reduction in the off-peak, however, was overpredicted, as it was also in the Stockholm case. To analyse congestion charges in Stockholm it is necessary and fully possible to integrate DTA with the demand model. In the performed tests it could be seen that both tested models had problems replicating the flow on the main bypass early in the morning but otherwise performed well. A case study of a metro extension in Stockholm demonstrated that congestion effects constitute more than half of the total benefits and that these effects are excessively underestimated by a conventional static model. Effects of various operational measures can be analysed with BusMezzo and the results have been validated against observed data. The findings indicate that all three tested measures in a case study (boarding through all doors, headway-based holding and bus lanes) had an overall positive impact on service performance and that there are synergetic effects.

Using a continuous VTT distribution and hierarchical route choice was demonstrated as a successful method of modelling the multi-passage rule implemented in Gothenburg congestion charges and was shown to give realistic predictions of route choice effects. First results from integration of DTA with a travel demand model for the Stockholm region show that even without systematic calibration the DTA is in reasonable agreement with observed traffic counts and travel times. The presented experiments did not reveal a striking difference between using a macroscopic and a microscopic assignment package. While travel time savings are often the only benefit included in public transport project appraisals, the best practice assigns weighted value of time to average load/capacity measures. However, failure to represent dynamic congestion effects may lead to substantial underestimation of the benefits of projects primarily designed to increase capacity rather than reduce travel times. The impact of small operational measures should not be underestimated. These measures are relatively cheap compared to investments in new transit infrastructure and large societal gains can therefore be achieved by their implementation.

Abstract [sv]

Investeringar och åtgärdsprogram inom transportområdet handlar allt oftare om att råda bot på trängsel snarare än att minska potentiella friflödesrestider. Utvärderingsmetoder för projekt som syftar till att minska trängsel är dock mindre utvecklade än metoder för projekt som syftar till att minska restider. Statiska nätutläggningsmodeller är till exempel inte lämpade för att prognosera uppbyggnad och avveckling av köer eller för att fånga upplevd trängsel orsakad av ojämn belastning på kollektivtrafikfordon. Trots förekomsten av dynamisk trafikutläggning och trots tämligen konkret kunskap om hur integration med efterfrågemodeller kunde gå till, finns det endast ett fåtal modellsystem utvecklade för verklig tillämpning.

Den predikterade trafikflödesminskningen på 11 % över trängselskattesnittet i Göteborg visade sig stämma väl överens med den observerade minskningen på 12 %. Minskningen under lågtrafik visade sig dock vara överskattad, precis som i Stockholmsfallet. För att analysera trängseleffekter i Stockholm är det nödvändigt och fullt möjligt att integrera en DTA-modell med efterfrågemodellen. I de utförda testerna observerades att båda de testade modellerna hade problem med att återskapa korrekta flöden på Essingeleden under morgonens maxtimme, men i övrigt gav god överensstämmelse. I en fallstudie av blå tunnelbanelinjes förlängning i Stockholm visade det sig att trängseleffekter utgjorde mer än hälften av de totala nyttorna och att dessa effekter är kraftigt underskattade i en konventionell statisk modell. Effekter av olika operationella åtgärder kan analyseras med BusMezzo och resultaten har blivit validerade mot observerade data. Resultaten tyder på att alla tre testade åtgärder i en fallstudie (ombordstigning i alla dörrar, turtäthetsbaserad reglering och busskörfält) hade en positiv inverkan på servicenivån och att det förekommer synergieffekter dem emellan.

Användandet av kontinuerlig tidsvärdesfördelning och hierarkiskt ruttval har framgångsrikt demonstrerats som en metod för att modellera flerpassageregeln i Göteborgs trängselskattesystem och visade sig ge realistiska prediktioner av ruttvalseffekter. De första resultaten från integrationen DTA i efterfrågemodellen för Stockholmsregionen visar att även utan systematisk kalibrering är modellresultaten i paritet med observerad trafikflöden och restider. Experimentresultaten tyder inte på någon slående skillnad mellan att använda makroskopisk eller mikroskopisk nätutläggning. Restidsvinst är ofta är den enda nyttan som ingår i nyttokalkylen för kollektivtrafikinvesteringar, men i visa fall är det befogat att använda viktade tidsvärden beroende på förhållandet belastning / kapacitet. Att inte modellera dynamiska trängseleffekter kan dock leda till påtagbar underskattning av nyttorna i projekt som primärt handlar om kapacitetshöjning snarare än restidsförkortning. Nyttan av små operationella åtgärder ska inte underskattas. Dessa åtgärder är oftast relativt billiga jämfört med investeringar i ny transportinfrastruktur och stora sociala nyttor kan därför åstadkommas.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , 25 p.
Series
TRITA-TSC-LIC, ISSN 1653-445X ; 15:003
National Category
Transport Systems and Logistics
Research subject
Transport Science
Identifiers
URN: urn:nbn:se:kth:diva-167416ISBN: 978-91-87353-73-4 (print)OAI: oai:DiVA.org:kth-167416DiVA: diva2:813376
Presentation
2015-06-08, Nash/Wardrop, L1, KTH, Drottning Kristinas väg 30, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-05-22 Last updated: 2016-08-25Bibliographically approved
List of papers
1. Ex-post evaluation of national transport model: Gothenburg congestion charges application
Open this publication in new window or tab >>Ex-post evaluation of national transport model: Gothenburg congestion charges application
2014 (English)Report (Other academic)
Alternative title[en]
Forecasting effects of congestion charges
Series
CTS working paper, 2016:9
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-168291 (URN)
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-06-01 Last updated: 2016-08-18Bibliographically approved
2. Integration of dynamic traffic assignment with a travel demand model for the Stockholm region
Open this publication in new window or tab >>Integration of dynamic traffic assignment with a travel demand model for the Stockholm region
Show others...
2014 (English)Conference paper, Oral presentation only (Other academic)
Publisher
112 p.
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-168292 (URN)
Conference
DTA 2014 conference in Salerno, Italy
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-06-01 Last updated: 2016-08-25Bibliographically approved
3. Appraisal of increased public transport capacity: The case of a new metro line to Nacka, Sweden
Open this publication in new window or tab >>Appraisal of increased public transport capacity: The case of a new metro line to Nacka, Sweden
2014 (English)Report (Other academic)
Series
CTS working paper, 2015:2
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:kth:diva-168293 (URN)
Conference
hEART Conference 2014 in Leeds, UK
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-06-01 Last updated: 2016-08-18Bibliographically approved
4. Individual and Synergetic Effects of Transit Service Improvement Strategies: Simulation and Validation
Open this publication in new window or tab >>Individual and Synergetic Effects of Transit Service Improvement Strategies: Simulation and Validation
2017 (English)In: Journal of transportation engineering, ISSN 0733-947X, E-ISSN 1943-5436, Vol. 143, no 6Article in journal (Refereed) Published
Abstract [en]

Assessment of transit service improvements such as bus lanes, allowing boarding through all doors, and headway-based holding control requires detailed simulation capabilities. However, because the usage of models advanced enough to simultaneously analyze physical and operational measures has been limited, their validity has hitherto remained low. This paper assesses the implementation of several bus service improvement measures in a simulation model. The paper analyzes the effect of isolated and combinations of measures, and validates the model using field experiment data. The model predicted travel time improvements accurately (1–2% difference), while overestimating some of the headway variability effects. The three tested measures exercised negative synergy effects, with their combined effect being smaller than the sum of their marginal contributions, except for headway-based holding, which exercised positive synergy effects with the two other measures.

National Category
Transport Systems and Logistics
Research subject
Transport Science
Identifiers
urn:nbn:se:kth:diva-168295 (URN)10.1061/JTEPBS.0000095 (DOI)
Funder
Stockholm County Council
Note

QC 20150601

Available from: 2015-06-01 Created: 2015-06-01 Last updated: 2017-10-10Bibliographically approved

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