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  • 1. Almstrom, Peter
    et al.
    Rabi, Maben
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Networked state estimation over a Gilbert-Elliot type channel2009In: Proceedings of the IEEE Conference on Decision and Control, 2009, p. 2711-2716Conference paper (Refereed)
    Abstract [en]

    We characterize the stability and achievable performance of networked estimation under correlated packet losses described by the Gilbert-Elliot model. For scalar continuous-time linear systems, we derive closed-form expressions for the mean-square distortion of the optimal estimator. The conditions for stable mean square estimation error are equivalent to those obtained previously for stability of 'peak distortions' [3]. We study how the estimator performance depends on loss probability and loss burst length, and show that the mean-square distortion remains bounded if the average burst length does not exceeda calculated bound. The main new finding is that, once we fix the mean length of loss bursts, the average packet loss rate influences the estimator's performance but not its stability. 

  • 2.
    Almström, Peter
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System analysis and economics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Three essays on transport CBA uncertainty2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cost Benefit Analysis (CBA) has for a long time been used in transport planning, but it is often questioned. One main argument against CBA is that the results depend largely on assumptions regarding one or a few input factors, as for example the future fuel price or valuation of CO2 emissions.

    The three papers included in this thesis investigate some aspects of uncertainty in transport CBA calculations. The two first papers explore how changes in input data assumptions affect the CBA ranking of six rail and road investments in Stockholm. The first paper deals with the effect of different land-use assumptions while the second deals with the influence of economic growth, driving cost and public transport fare. The third paper investigates how alternative formulations of the public transport mode choice and route choice affect travel flows, ticket revenues and consumer surplus. These are important factors previously known to affect CBA results.

    The findings of the first two papers suggest that CBA results are robust concerning different land-use scenarios and single input factors. No change in rank between a road and a rail object is observed in the performed model calculations, and only one change between two road objects. The fact that CBA results seem robust regarding input assumptions supports the use CBA as a tool for selecting transport investments. The results in the third paper indicate that if there is detailed interest in, for example, number of boardings and ticket income from a certain transit line, or the total benefit of a price change, a more detailed formulation of the public transport mode choice and route choice will provide more reliable results. On the other hand, this formulation requires substantially more data on the transit line and price structure than the conventional formulation used in Swedish transport planning, especially in areas with many different pricing systems.

  • 3. Almström, Peter
    et al.
    Berglund, Svante
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Börjesson, Maria
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Jonsson, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Land use planning and transport investment appraisal2011Conference paper (Refereed)
  • 4. Almström, Peter
    et al.
    Berglund, Svante
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Börjesson, Maria
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Jonsson, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    The impact of land use planning on Cost-Benefit Analysis rankings2011In: Proceedings of the European Transport Conference, 2011Conference paper (Refereed)
  • 5.
    Almström, Peter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Berglund, Svante
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Börjesson, Maria
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Jonsson, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    The impact of travel costs and economic growth on cost-benefit analysis rankings2012Manuscript (preprint) (Other academic)
    Abstract [en]

    The use of Cost-benefit analysis (CBA) as a tool for selecting transport investments is often questioned. It is not unusual that politicians or others in the public debate argue that the outcome of a CBA completely rely on assumptions concerning a particular input factor, such as valuation of CO2 emissions or future fuel price. This paper explores whether the relative ranking of CBA outcomes are robust with respect to some key inputs in transport demand analysis driving cost, public transport fare and economic growth. We study six different infrastructure objects (three road and three rail objects) and four alternative assumptions on input factors compared to a reference scenario.

    The findings suggest that single input factors in a CBA, individually have a small impact on the ranking of the studied investments. In our model calculations we observe no change in rank between a road and a rail object.

  • 6.
    Almström, Peter
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Engelson, Leonid
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Algers, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Modelling the effect of transit supply and price structure on mode choice and route choice2011Conference paper (Refereed)
    Abstract [en]

    This paper develops a new mode choice and transit route choice model for work trips by either car or transit. In contrast to the conventional regional traffic models used for transportation planning in Sweden, the model accounts for the fact that the value of time varies within a population of travellers making a trip with the same purpose and the fact that the price can differ between different transit lines (bus, regional trains, etc.). A mixed binomial logit (MXL) model with a lognormally distributed cost parameter has been estimated for the mode choice. The MXL specification makes it possible to capture some of the variation in the value of time. The transit route choice model rests on the assumption that transit commuters purchase travel passes that are valid for a certain time period, e.g. a month. The travel pass then allows the traveller to use a certain set of transit lines, while others are not available. For the mode choice, the traveller compares travel cost and time with the chosen pass with the travel cost and time by car. The results from performed analyses indicate that if the interest is in overall mode share and overall travel flows, the conventional method in Swedish transport modelling will suffice. However, if the interest is more detailed, for example concerning boardings and ticket income from a certain transit line, or the total benefit of a price change, the model developed in this paper will give more reliable results.

  • 7.
    Börjesson, Maria
    et al.
    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.
    Jonsson, R. Daniel
    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.
    Berglund, Svante
    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.
    Almstrom, Peter
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System analysis and economics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Land-use impacts in transport appraisal2014In: Research in Transportation Economics, ISSN 0739-8859, E-ISSN 1875-7979, Vol. 47, p. 82-91Article in journal (Refereed)
    Abstract [en]

    Standard cost-benefit analysis (CBA) does not take into account induced demand due to relocation triggered by infrastructure investments. Using an integrated transport and land-use model calibrated for the Stockholm region, we explore whether this has any significant impact on the CBA outcome, and in particular on the relative ranking of rail and road investments. Our results indicate that induced demand has a larger impact on the benefit of rail investments than on the benefit of road investments. The effect on the relative ranking is still limited for two reasons. First, the number of houses that are built over 20 30 years is limited in comparison to the size of the existing housing stock. Second, the location of most of the new houses is not affected by any single infrastructure investment, since the latter has a marginal effect on total accessibility in a city with a mature transport system. A second aim of this paper is to investigate the robustness of the relative CBA ranking of rail and road investments, with respect to the planning policy in the region 25 years ahead. While the results suggest that this ranking is surprisingly robust, there is a tendency that the net benefit of rail investments is more sensitive to the future planning policy than road investments. Our results also underscore that the future land-use planning in the region in general has a considerably stronger impact on accessibility and car use than individual road or rail investments have.

  • 8.
    Jonsson, Daniel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Berglund, Svante
    Almström, Peter
    Algers, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    The Usefulness of Transport Models in Swedish Planning Practice2011In: Transport reviews, ISSN 0144-1647, E-ISSN 1464-5327, Vol. 31, no 2, p. 251-265Article in journal (Refereed)
    Abstract [en]

    This paper presents some experience from using transport models in Swedish planning practice. First we outline three recent examples of planning settings in which transport models have been put to extensive use. For the Swedish ‘national’ transport plan for the period 2010–2021, which was recently finished, the national transport model SAMPERS was used to compute costs and benefits for many investment projects. The second example concerns the ‘regional’ plan for Stockholm, where a similar but less detailed model, LuTRANS, was used to investigate different transport and land use scenarios. The third example discusses a recent study on the feasibility of introducing congestion charges in Gothenburg, where both a fixed demand approach and SAMPERS were used. Furthermore, the paper tries to help identify what model development can do to help improve the production of decision support through modelling. We argue that effectiveness and efficiency are key. The first is characterized by making sure that the right things are done and that they are done right. Efficiency, which is less often discussed in the literature, is framed in terms of doing things on time and doing them only once. The managing organization around a national model system can play an important role in helping users avoid redundant work. It is also a good idea to resist the temptation to use up all improvements in computing power for additional model features. There are many worthwhile analyses that are never done because of time constraints.

  • 9. Pereira, Paulo Rogério
    et al.
    Grilo, António
    Rocha, Francisco
    Nunes, Mário Serafim
    Casaca, Augusto
    Chaudet, Claude
    Almström, Peter
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    End-to-end reliability in wireless sensor networks: survey and research challenges2007In: EuroFGI workshop on IP QoS and Traffic Control / [ed] P. Pereira, 2007Conference paper (Other academic)
    Abstract [en]

    This paper presents a survey on transport and routing protocols for wireless sensor networks(WSN). Research challenges regarding the problem of end-to-end reliability are addressed in particular.

  • 10.
    Rabi, Maben
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Stabellini, Luca
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Almström, Peter
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Analysis of networked estimation under contention-based medium access2008In: 17th World Congress, International Federation of Automatic Control, IFAC, 2008Conference paper (Refereed)
    Abstract [en]

    We treat a problem in networked estimation where the focus is on sampling and transmitting measurements of the plant over a shared medium. The object is to choose the sampling rate at the sensor while taking the statistics of a contention based MAC protocol into account. In particular, we seek a trade-off between the reliable delivery of individual data packets and the input data load on the communication medium. Our analysis of the shared channel computes a probability of packet loss for an assumed IID loss process. This loss rate depends on the input packet stream intensities. We compute the estimation distortion with IID losses of periodically generated samples, as a function of the packet loss rate. This throws up a condition for stable estimator performance. We investigate the scalability limits of this stability as a function of the number of nodes. When stable estimation is possible, we provide a procedure that computes the input packet rate for the network that minimizes the average estimation distortion. We reproduce the analysis of estimation performance when the sensors sample asynchronously according to independent Poisson counters.

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