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  • 1.
    Abdollahzadeh, Makan
    et al.
    K.N.Toosi University of Technology, Faculty of Geodesy and Geomatic Engineering, Tehran, Iran.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Geodesy (closed 20110301).
    Najafi, Mehdi
    K.N.Toosi University of Technology, Faculty of Geodesy and Geomatic Engineering, Tehran, Iran.
    A semi-vectorization algorithm to synthesis of gravitational anomaly quantities on the Earth's surface2009Conference paper (Refereed)
    Abstract [en]

    The Earth’s gravitational potential can be expressed by the well-known spherical harmonic expansion. The computationaltime of summing up this expansion is an important practical issue which can be reduced by an efficientnumerical algorithm. This paper proposes such a method for block-wise synthesizing the anomaly quantities onthe Earth surface using vectorization.Fully-vectorization means transformation of the summations to the simple matrix and vector products. It is not apractical for the matrices with large dimensions. Here a semi-vectorization algorithm is proposed to avoid workingwith large vectors and matrices. It speeds up the computations by using one loop for the summation either ondegrees or on orders. The former is a good option to synthesize the anomaly quantities on the Earth surfaceconsidering a digital elevation model (DEM). This approach is more efficient than the two-step method whichcomputes the quantities on the reference ellipsoid and continues them upward to the Earth surface. The algorithmhas been coded in MATLAB which synthesizes a global grid of 50 x 50 (corresponding 9 million points) of gravityanomaly or geoid height using a geopotential model to degree 360 in 10000 seconds by an ordinary computer with2G RAM.

  • 2. Acs, Zoltan J.
    et al.
    Braunerhjelm, Pontus
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Economics.
    Audretsch, David B.
    Carlsson, Bo
    The knowledge spillover theory of entrepreneurship2009In: Small Business Economics, ISSN 0921-898X, E-ISSN 1573-0913, Vol. 32, no 1, p. 15-30Article in journal (Refereed)
    Abstract [en]

    Contemporary theories of entrepreneurship generally focus on the recognition of opportunities and the decision to exploit them. Although the entrepreneurship literature treats opportunities as exogenous, the prevailing theory of economic growth suggests they are endogenous. This paper advances the microeconomic foundations of endogenous growth theory by developing a knowledge spillover theory of entrepreneurship. Knowledge created endogenously results in knowledge spillovers, which allow entrepreneurs to identify and exploit opportunities.

  • 3.
    Algers, Staffan
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    What is the monetary value of security?2010Conference paper (Other academic)
  • 4.
    Algers, Staffan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Eliasson, Jonas
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Is it time to use activity-based urban transport models? A discussion of planning needs and modelling possibilities2005In: The annals of regional science, ISSN 0570-1864, E-ISSN 1432-0592, Vol. 39, no 4, p. 767-789Article in journal (Refereed)
    Abstract [en]

    For some decades now, transport researchers have put considerable efforts into developing what is called activity-based approaches for modelling urban travel demand. The basic idea is that travel demand is derived from people's desires to take part in different activities. In particular, the interrelationships among different activities with respect to temporal and spatial constraints are in focus. It means that such models treat the activities and the travelling of the households with respect to where and when the activities can be carried out and how they may be scheduled, given characteristics of the households and potential opportunities, the transport networks and various institutional constraints. We discuss what demands we see on future travel demand models, with a focus on urban analysis. This discussion is somewhat biased towards what role activity-based models could play in meeting these demands. We then review in some detail three prominent and distinctly different representatives of operational activity-based models to give an indication of what new modelling possibilities they offer. Theoretical appeal, empirical validity, usefulness for planning, need for data and easiness of implementation are discussed. In the final section we draw some conclusions about the prospects of these models and of their descendants.

  • 5.
    Algers, Staffan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Mattsson, Lars-Göran
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Rydergren, Clas
    Östlund, Bo
    Sampers: erfarenheter och utvecklingsmöjligheter på kort och lång sikt2009Report (Other academic)
  • 6.
    Algers, Staffan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Sundbergh, P.
    Byström, C.
    Valuation of road traffic noise profiles2009In: 38th International Congress and Exposition on Noise Control Engineering 2009, INTER-NOISE 2009, 2009, p. 2161-2168Conference paper (Refereed)
    Abstract [en]

    Swedish noise values are today based on a study concerning hedonic price values. The valuation of the average noise levels assumes that there is no difference between different noise profiles, i.e. how the noise level varies throughout the day. In order to be able to take appropriate measures towards noise problems, it is important to know to what extent the noise profile matters. The project aims at researching how the noise value depends on the road traffic noise profile. It further aims at studying how values are affected by the type of activity in which the noise disturbance occurs (being out in the garden/try to sleep in the bedroom). Our method is to use stated preference techniques (pair wise choices) to elicit noise profile values. Respondents listen to and evaluate noise profile where we vary the level of background noise, frequency of noise events and the noise level of the events. This paper also discusses possibilities to estimate willingness to pay for changes in different components of noise profiles.

  • 7. Allgulander, Christer
    et al.
    Näsman, Per
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Safety Research.
    Regular hypnotic drug treatment in a sample of 32,679 Swedes: associations with somatic and mental health, inpatient psychiatricdiagnoses and suicide, derived with automated record-linkage1991In: Psychosomatic Medicine, ISSN 0033-3174, E-ISSN 1534-7796, Vol. 53, no 1, p. 101-108Article in journal (Refereed)
    Abstract [en]

    We studied Swedish survey responders who reported regular treatment with hypnotic drugs, to find associations to perceived health problems, inpatient psychiatric diagnoses, and subsequent suicide. Among 32,679 sampled Swedes, 26,952 (83%) participated, 500 of which (2%) reported regular hypnotic drug treatment. The rate of treatment was higher in women, and increased by age in both sexes. The major findings were high odds of concurrent psychoactive drug treatments, nervous symptoms and insomnia, as well as high rates of circulatory and musculoskeletal conditions in both sexes, with indicators of disability and sleep-disturbing symptoms. During a 15-year period, 35% of the men and 21% of the women who reported regular hypnotic drug treatment had also been admitted to inpatient psychiatric care. Substance abuse was diagnosed in 20% of the men and 4.3% of the women reporting hypnotic drug treatment. In multiple logistic regression models, the highest odds for regular hypnotic drug treatment were incurred by recent/current insomnia, nervous symptoms, and other psychoactive drug treatment. We conclude that therapy was principally given according to some current peer guidelines. Yet, further research is needed into the risk/benefit ratio of sustained hypnotic drug therapy in patients with qualifying somatic and psychiatric disorders to obtain a more uniformly based consensus.

  • 8.
    Al-Mudhaffar, Azhar
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Impacts of Traffic Signal Control Strategies2006Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    Traffic signals are very cost effective tools for urban traffic management in urban areas. The number of intersections in Sweden controlled by traffic signals has increased since the seventies, but efforts to study the traffic performance of the employed strategies are still lacking. The LHOVRA technique is the predominant isolated traffic signal control strategy in Sweden. Past-end green was originally incorporated as part of LHOVRA (the “O” function) and was intended to reduce the number of vehicles in the dilemma zone. Coordinated signal control in Sweden is often fixed-time with local vehicle actuated signal timing adjustments and bus priority. This research study was undertaken to increase the knowledge of the traffic performance impacts of these strategies.

    The aim was to evaluate the following control strategies using Stockholm as a case study:

    1. The LHOVRA technique with a focus on the “O” function;

    2. Fixed time coordination (FTC);

    3. Fixed time coordination with local signal timing adjustment (FTC-LTA);

    4. FTC-LTA as above + active bus priority (PRIBUSS);

    5. Self-optimizing control (SPOT).

    Field measurements were used for study of driver behavior and traffic impacts as well as for collecting input data needs for simulation. The results from low speed approaches showed a higher proportion of stopped vehicles after receiving green extension. Moving the detectors closer to the stop line, and/or making the detectors speed dependent were suggested as measures to solve these problems. The VISSIM simulation model calibrated and validated with empirical data was used to study traffic performance and safety impacts of the LHOVRA technique as well as to test the suggested improvements. The simulation experiment results from these design changes were shown to reduce accident risk with little or no loss of traffic performance.

    TRANSYT was used to produce optimized fixed signal timings for coordinated intersections. HUTSIM simulations showed that local signal timing adjustment by means of past-end green was beneficial when applied to coordinated traffic signal control in the study area. Both delays and stops were reduced, although not for the main, critical intersection which operated close to capacity.

    To study the impacts of strategies for coordinated signal control with bus priority, extensive field data collection was undertaken during separate time periods with these strategies in the same area using mobile and stationary techniques. A method to calculate the approach delay was developed based on the observed number of queuing vehicles at the start and end of green. Compared to FTC-LTA, the study showed that PRIBUSS reduced bus travel time. SPOT reduced both bus and vehicle travel time.

    Future research efforts for the development of signal control strategies and their implementation in Sweden should be focused on strategies with self-optimization functionality.

  • 9. Anand, N.
    et al.
    Anayi, Michel
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Improving punctuality of train traffic on Western main line of Swedish railway network: Simulation approach2010In: Proceedings Of The ASME Rail Transportation Division Fall Conference 2009, ASME Press, 2010, p. 15-24Conference paper (Refereed)
    Abstract [en]

    Western main line is one of the most important railway lines in Sweden. The line section from Stockholm to Katrineholm, which connects the largest cities of the Sweden i.e. Stockholm, Gothenburg and Malmö, is studied. This line has heterogeneous train traffic consisting high-speed, regional, freight and commuter trains. This paper attempts to study different factors affecting punctuality on this railway line concentrating on traffic problem around Gnesta station and commuter train turn-back scenario - a bottleneck - at the same station. Simulation of existing and modified timetable is done using train traffic simulation software "Railsys". Experiments including examining effect of rescheduling train timings, capacity enhancement and infrastructure changes in rail network are conducted and investigated. Robustness analysis is performed from the results of simulation and investigation of the consequences of delays and comparison of how different features in the timetables affect the robustness is done.

  • 10.
    Andersson, Henrik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Perception of Own Death Risk: A Reassessment of Road-Traffic Mortality Risk2008Report (Other academic)
    Abstract [en]

    This study examines individuals' perception of their own road-mortality risk. Swedish data on respondents' subjective risk beliefs is used and compared with objective risk estimates. The objective risk is defined as the risk of the respondent's own age and gender group, and it is found that low and high risk groups over- and underassess their risk levels, respectively. This study replicates the analysis used by Andersson and Lundborg (2007) and the pattern of over- and underassessment found confirms their findings. As in their study, risk beliefs are updated in line with the Bayesian learning model, a relationship not statistically significant in this study, though. Regarding results of individual characteristics and risk beliefs in both studies, whereas, e.g., gender effects are robust, other results suggest a weak relationship between the perception of own road-mortality risk and individual characteristics.

  • 11.
    Andersson, Henrik
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Private and Public WTP for Safety: A Validity Test2007Report (Other academic)
    Abstract [en]

    To elicit an affected population's preferences for, e.g., better health or environment stated preference (SP) methods are often used. SP methods are based on hypothetical market settings which necessitates validity tests of the results. This study describes a validity test on the basis of theoretical predictions and empirical findings for private and public safety measures. According to the test, public willingness to pay (WTP) should exceed private WTP.

  • 12.
    Andersson, Johan Vium
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Geodesy.
    A Complete Model for Displacement Monitoring Based on Undifferenced GPS Observations2008Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    During recent years there has been a great focus on the climate changes within the media. More or less every day more newspaper articles are presented about the global warming issue and the effect on us human race. Climate models predict higher temperatures and more rain in the northern part of Europe. It is also predicted that the weather will become more extreme e.g. it will rain a lot during longer periods than has been the norm. If these predictions are correct, the amount of water that is going to be transported away in streams and rivers will increase and so also will the subsoil water level. The latter increases the risk for landslides in areas with fine grained soils. An early warning system that is able to alert people before a landslide take place would be of great interest.

    The purpose of this work is to develop a complete real-time displacement monitoring system based on observations from several GPS-receivers that could be used as an early warning system. Due to the complex correlation structure of the traditionally used double differences, an alternative method based on undifferenced observations is used. Theoretically this approach shows some advantages and simplifies the correlative structure of observables compared to the double differenced method. A complete model for the undifferenced approach is presented in this thesis including its software implementation.

    A displacement detection system includes not only the positioning algorithms, but also methods to detect if any displacement occurs. There are many methods available to discriminate displacements, which are used in the traditional control of manufacturing processes. Several of these methods are compared in this thesis, such as the Shewhart chart, different Weighted Moving Average (WMA) charts and the CUmulative SUMmation (CUSUM). Practical tests show that it is possible to detect an abrupt shift on sub centimetre level at the same epoch as the shift occurs. Smaller shifts are also detectable with the applied approach but with a slightly longer detection time.

  • 13.
    Andersson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Co-location of Manufacturing and Producer Services: A simultaneous equations approach2006In: Entrepreneurship and Dynamics in the Knowledge Economy, Routledge , 2006, p. 94-124Chapter in book (Other academic)
  • 14.
    Andersson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Industrial Agglomeration and New Technologies: a global perspective – Edited by Masatsugu Tsuji, Emanuele Giovannetti and Mitsuhiro Kagami2008In: Papers in regional science (Print), ISSN 1056-8190, E-ISSN 1435-5957, Vol. 87, no 1, p. 147-149Article, book review (Refereed)
  • 15.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Ejermo, Olof
    How does Accessibility to Knowledge Sources Affect the Innovativeness of Corporations?: Evidence from Sweden2005In: The annals of regional science, ISSN 0570-1864, E-ISSN 1432-0592, Vol. 39, no 4, p. 741-765Article in journal (Refereed)
    Abstract [en]

    This paper studies the innovative performance of 130 Swedish corporations during 1993-1994. The number of patents per corporation is explained as a function of the accessibility to internal and external knowledge sources of each corporation. A coherent way of handling accessibility measures, within and between corporations located across regions, is introduced. We examine the relative importance of intra- and interregional knowledge sources from 1) the own corporation, 2) other corporations, and 3) universities. The results show that there is a positive relationship between the innovativeness of a corporation and its accessibility to university researchers within regions where own research groups are located. Good accessibility among the corporation's research units does not have any significant effects on the likelihood of generation of patents. Instead the size of the R&D staff of the corporation seems to be the most important internal factor. There is no indication that intraregional accessibility to other corporations' research is important for a corporation's innovativeness. However, there is some indication of reduced likelihood for own corporate patenting when other corporate R&D is located in nearby regions. This may reflect a negative effect from competition for R&D labor.

  • 16.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Ejermo, Olof
    Technology Specialization and the Magnitude and Quality of Exports2008In: Economics of Innovation and New Technology, ISSN 1043-8599, E-ISSN 1476-8364, Vol. 17, no 4, p. 355-375Article in journal (Refereed)
    Abstract [en]

    This paper examines howtechnologyspecialization, measured by citation-weighed patents, affects trade flows. The paper analyzes the relationship between (i)technologyspecializationandexportspecializationacross regions and (ii) thetechnologyspecializationof origin and destination and thequalityofexportflows. We find that theexportspecializationof regions corresponds to theirtechnologyspecialization. Regions with highertechnologyspecializationexportproducts of higherquality, as indicated by higher prices. Moreover,exportflows to destination countries with a hightechnologyspecializationconsist of products of higherqualityin the specifictechnology. The results are consistent with knowledge andtechnologybeing important forexportperformance and with regions with higherspecializationin atechnologybeing better equipped to produce high-qualityproducts. They are also consistent with destinations of highertechnologyspecialization, having a more pronounced demand for products of higherqualityin the sametechnology.

  • 17.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Gråsjö, U.
    Karlsson, C.
    Knowledge, Knowledge Flows and Regional Growth: An analysis of the importance of knowledge accessibility2007In: ICFAI Journal of Knowledge Management, ISSN 0972-9216, Vol. 5, no 4, p. 7-26Article in journal (Refereed)
  • 18.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Gråsjö, Urban
    Karlsson, Charlie
    Human Capital and Productivity in a Spatial Economic System: relating the extent of spatial dependence to localities’ position2008In: Annales d'Economie et Statistique, ISSN 0769-489X, no 87/88, p. 125-144Article in journal (Refereed)
  • 19.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Gråsjö, Urban
    Karlsson, Charlie
    University and Industry R&D Accessibility and Regional Growth2008In: Scienze Regionali, ISSN 1720-3929, Vol. 7, no 2, p. 97-115Article in journal (Refereed)
    Abstract [en]

    A shortcoming of traditional endogenous growth approaches is their assumption that the stock of knowledge is generally accessible across space. The purpose of this paper is to analyse the contribution of R&D to economic growth in Swedish municipalities, taking account of the variation in R&D accessibility among different municipalities. We argue that the interaction possibilities at different spatial scales can be properly represented by an accessibility approach which discounts interaction potentials using travel time distances. The main result of the analysis is that knowledge accessibility in a given period has a statistically significant effect on the growth in value-added per employee in subsequent periods. Furthermore, the knowledge resources in a given municipality tend to have a positive effect on the growth of another municipality, conditional on the municipalities belonging to the same functional region.

  • 20.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301). KTH, School of Industrial Engineering and Management (ITM), Centres, Centre of Excellence for Science and Innovation Studies, CESIS.
    Johansson, Börje
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301). KTH, School of Industrial Engineering and Management (ITM), Centres, Centre of Excellence for Science and Innovation Studies, CESIS.
    Innovation Ideas and Regional Characteristics: product innovations and export entrepreneurship by firms in Swedish regions2008In: Growth and Change, ISSN 0017-4815, E-ISSN 1468-2257, Vol. 39, no 2, p. 193-224Article in journal (Refereed)
    Abstract [en]

    This paper focuses upon the ways in which characteristics of regions in regards to knowledge sources, communication opportunities, and absorptive capacity influence the development of innovation ideas among existing and potential entrepreneurs. We formulate a model where entrepreneurs or innovating firms introduce new products in a quasi-temporal setting. Market conditions are characterised by monopolistic competition between varieties belonging to the same product group, in which there is entry and exit of varieties. A stochastic process is assumed to generate new innovation ideas as time goes by, and a firm (entrepreneur) who receives such an idea has to transform the idea to an innovation, which in the model is specified as a particular variety combined with a specific destination market. The theoretical model is used as a reference when formulating two regression models, with which we estimate how a set of regional characteristics are associated with the likelihood of innovation ideas across Swedish local labour market regions. In one model, we examine the emergence of new export varieties, and in the second model, we investigate the appearance of new export firms. Results are consistent with the assumption that knowledge and information flows have a positive influence on the frequency of arrival of innovation ideas to firms.

  • 21. Andersson, Martin
    et al.
    Johansson, Börje
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Economics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre of Excellence for Science and Innovation Studies, CESIS (closed 20110701).
    Månsson, Kristofer
    Dynamics of Entry and Exit of Product Varieties: – what evolution dynamics can account for the empirical regularities?2009Report (Other academic)
    Abstract [en]

    Firm-level heterogeneity is substantial even in narrowly defined industries. This paper focuses on formulating evolution dynamics which can account for the observed heterogeneity and its maintenance. Based on examination of data on Swedish firm’ supply pattern to different markets over time, we present a parsimonious model that has the ambition to capture the picture of heterogeneous firms, while accommodating the simultaneous exit and entry of destination varieties in firms’ supply pattern. The model assumes both scale economies of firms and pathdependence, where the latter is manifested in such a way that the arrival rate of innovation ideas to an individual firm is a function of each firm’s stock of varieties at every given point in time. The path-dependence phenomenon is an “explosive” non-linearity, whereas conservation mechanisms include development of demand and exit of established varieties. The described path dependence explains the skewed distribution of varieties across firms, but the question of what keeps the “equilibrium” away from competitive exclusion where only few large firms remain. We make use of simulations to depict and assess the innovation dynamics of the proposed model.

  • 22.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Karlsson, Charlie
    Regional innovation systems in small and medium-sized regions: A critical review and assessment2006In: The Emerging Digital Economy: Entrepreneurship, Clusters and Policy, Springer-Verlag , 2006, p. 55-82Chapter in book (Other academic)
  • 23.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Karlsson, Charlie
    The Location of Industry R&D and the Location of University R&D: how are they related?2008In: Innovation, Dynamic Regions and Regional Dynamics, Berlin: Springer , 2008Chapter in book (Other academic)
  • 24.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Klaesson, Johan
    Growth Dynamics in a Municipal Market-Accessibility Hierarchy: Does the ICT service sectors follow the overall pattern?2006In: The Emerging Digital Economy: Entrepreneurship, Clusters and Policy, Springer-Verlag , 2006, p. 187-214Chapter in book (Other academic)
  • 25.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Klaesson, Johan
    Regional Interaction and Economic Diversity: exploring the role of geographically overlapping markets for a municipality’s diversity in retail and durables2009In: Innovation, Agglomeration and Regional Competition, Edward Elgar , 2009Chapter in book (Other academic)
  • 26.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Lööf, Hans
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Economics (closed 20110301).
    Learning-by-Exporting Revisited: The Role of Intensity and Persistence*2009In: Scandinavian Journal of Economics, ISSN 0347-0520, E-ISSN 1467-9442, Vol. 111, no 4, p. 893-916Article in journal (Refereed)
    Abstract [en]

    Two non-mutually exclusive hypotheses can explain the empirically established export premium: self-selection of more productive firms into export markets and learning-by-exporting. This paper focuses on how the temporal dimension of firms' exporting activities and the intensity of exports influence the scope of learning effects. Using a panel of Swedish firms and dynamic generalized method of moments estimation, we find a learning effect among persistent exporters with high export intensity, but not among temporary exporters or persistent exporters with low export intensity. For small firms, exports boost productivity among persistent exporters with both high and low export intensity, but the effect is stronger for persistent export-intensive small firms.

  • 27.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre of Excellence for Science and Innovation Studies, CESIS.
    Lööf, Hans
    Johansson, Sara
    Productivity and International Trade: firm-level evidence from a small open economy2008In: Review of World Economics, ISSN 1610-2878, E-ISSN 1610-2886, Vol. 144, no 4, p. 774-800Article in journal (Refereed)
    Abstract [en]

    This paper presents a comprehensive description and analysis of the international trading activities of firms based on novel and detailed Swedish data. We provide robust evidence of selection operating from market to market which is consistent with that low productive firms are confined to markets with low productivity thresholds. We further show that selection also applies to the number of products traded. There is a substantial heterogeneity among exporters and importers in terms of the number of markets they trade with and in terms of the number of products they trade. Productivity premiums increase in the number of markets and the number of products traded, respectively. Firms that both export and import (i.e. two-way traders) are more productive than firms that only export or only import. This finding can be explained by that two-way traders are deeply engaged in the international division of labor and employ inputs based on frontier knowledge and technology in their production process, which increase their productivity and success on export markets.

  • 28.
    Andersson, Martin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Thulin, Per
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Globalisering, arbetskraftens rörlighet och produktivitet2008Report (Other academic)
    Abstract [sv]

    Teknologiska framsteg och kunskapsutveckling är den viktigaste förklaringen till högre tillväxt och ett ökat välstånd. I en dynamisk global ekonomi där teknikfronten flyttas framåt i allt snabbare takt blir därför förmågan att tillgodogöra sig ny teknik allt viktigare. Betydelsen av väl fungerande utbildningssystem och starka forskningsmiljöer för produktivitet och tillväxt är väl känt, däremot är kunskaperna beträffande hur kunskap sprids mellan företag och regioner betydligt mer begränsade. Genom att använda ett unikt datamaterial visar författarna att en ökad rörlighet av högutbildade har en positiv inverkan på produktiviteten. Tolkningen är att högutbildade är bärare av kunskap som sprids och kombineras med redan befintlig kunskap vilket i sin tur har positiva produktivitetseffekter. Flöden av arbetskraft mellan företag, regioner och länder blir en viktig komponent för att öka tillväxt och välstånd. Politiken bör därför utforma system som skapar goda förutsättningar för rörlighet samt reducerar inlåsningseffekter i den svenska ekonomin. Resultaten pekar också på att "täta" miljöer som storstäder och klusterbildningar är särskilt gynnsamma för kunskapsspridning, skapandet av humankapital, innovationer och tillväxt.

  • 29.
    Andersson, Mats
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Empirical Essays on Railway Infrastructure Costs in Sweden2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The subject of this thesis concerns pricing the use of transport infrastructure. We are empirically investigating the relationship between railway traffic volumes and infrastructure management costs. More specifically, we are interested in estimating the change in infrastructure management costs from marginal variations in traffic volumes, i.e. to estimate the marginal cost of railway infrastructure wear and tear. Both Europe and Sweden have moved towards a marginal cost based transport pricing policy, thus driving the need for more empirical work on rail infrastructure costs to underpin the level of a wear and tear charge. The thesis consists of five papers. In paper I, the data situation for planning railway maintenance and renewal is surveyed internationally. The survey indicates that most infrastructure managers are still in the data gathering phase, rather than ready to use modern computerised planning tools to make sound decisions in the field of maintenance and renewal. In paper II, we investigate the data situation for infrastructure cost analysis in Sweden. A panel data set that consists of cost, traffic and infrastructure information is created. The data covers 1999-2002 and contains almost 190 annual observations. Three main cost categories are identified; infrastructure operation, maintenance and renewal. This data is used for estimations of cost functions in paper II, III and V. Econometric techniques are applied for this purpose, with several different model specifications. In paper II, the method of pooled ordinary least squares (POLS) is applied. In paper III, we turn to unobserved effects models to exploit data heterogeneity. Finally in paper V, a dynamic generalised method of moments estimator is used to explore a potential dynamic cost dependency. The main findings are that the POLS approach, which has been used in similar studies in Europe recently, is rejected in favour of fixed effects estimation for this data. Furthermore, we also reject the idea of regression analysis to capture marginal rail renewal costs. In paper IV, we suggest an analytical expression combined with survival analysis of rail ages to estimate marginal renewal costs. We derive elasticities with respect to output as well as marginal costs for the different cost categories, and find that the current charge for wear and tear in Sweden is well below these new estimates. This opens up for increased, marginal cost based rail infrastructure wear and tear charges, which would reduce the financial burden on Swedish tax-payers.

  • 30.
    Andersson, Mats
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Fixed effects estimation of marginal railway infrastructure costs in Sweden2007Report (Other academic)
    Abstract [en]

    New railway legislation in Sweden has increased the need for transparent access charges on the Swedish railway network. We estimate cost functions for infrastructure operation, maintenance and renewal in the Swedish national railway network, using unobserved effects models and calculate marginal costs for railway infrastructure wear and tear. We find evidence of unobserved fixed effects at a track section level for infrastructure operation and maintenance costs. The estimated weighted average marginal infrastructure operation cost is SEK 0.12 per train kilometre and the estimated marginal maintenance cost is SEK 0.0073 per gross tonne kilometre. Altogether, the results indicate that the current charge for railway infrastructure wear and tear in Sweden is below marginal cost.

  • 31.
    Andersson, Mats
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Marginal cost pricing of railway infrastructure operation, maintenance, and renewal in Sweden: from policy to practice through existing data2006In: RAILWAYS, Washington D.C.: National research council. Transportation research board , 2006, no 1943, p. 1-11Conference paper (Refereed)
    Abstract [en]

    The separation of infrastructure and train operations in Europe's railway sector has increased the importance of a transparent policy for pricing infrastructure use. This paper reviews the quality of data on the Swedish railway network to allow estimation of the marginal costs of railway track wear and tear. Information about costs, traffic, and infrastructure is examined and assessed in light of an econometric modeling approach. The review shows that the basic data necessary to estimate an econometric cost function are not always at hand. In particular, no extensive time series data are available, and there are instances of partially missing data. However, some problems can be overcome through the use of data imputation techniques. A database covering 749 track section observations from 1999 to 2002 was created. Cost functions were estimated via pooled ordinary least squares, and marginal costs were calculated. Separate charging regimes for operational and maintenance costs are suggested, but more research is needed before renewal costs can be recommended for inclusion.

  • 32.
    Andersson, Mats
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Marginal railway infrastructure costs in a dynamic context2007In: European Journal of Transport and Infrastructure Research, ISSN 1567-7133, Vol. 8, no 4, p. 268-286Article in journal (Refereed)
    Abstract [en]

    In this paper, dynamic aspects of railway infrastructure operation and maintenance costs in Sweden are explored. Econometric cost functions are estimated to check the robustness of previous marginal cost estimates by introducing lags and leads of both dependent and independent variables. We find support for a forward-looking behaviour within the Swedish National Rail Administration (Banverket) as both infrastructure operation and maintenance costs are reduced prior to a major renewal. There are also indications of both lagged traffic and costs affecting the cost structure.

  • 33.
    Andersson, Mats
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Transport and Location Analysis (closed 20110301).
    Marginal railway renewal costs: a survival data approach2007In: Working papers, Vol. 10Article in journal (Other academic)
    Abstract [en]

    In this paper, renewal costs for railway tracks are investigated using survival analysis. The purpose is to derive the effect from increased traffic volumes on rail renewal cycle lengths and to calculate associated marginal costs. A flow sample of censored data containing almost 1 500 observations on the Swedish main railway network is used. We specify Weibull accelerated failure time regression models, and estimate deterioration elasticities for total tonnage as well as for passenger and freight tonnages separately. Marginal costs are calculated as a change in present values of renewal costs from premature renewal following increased traffic volumes.

  • 34. Antoniou, C
    et al.
    Balakrishna, R
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Emerging Data Collection Technologies and their Impact on Traffic Management Applications2008Conference paper (Refereed)
  • 35. Antoniou, C.
    et al.
    Balakrishna, R.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Exploiting emerging data collection technologies for dynamic traffic management applications2010In: Proceedings of World Conference on Transport Research (WCTR), 2010Conference paper (Refereed)
    Abstract [en]

    Several existing and emerging surveillance technologies are being used for traffic datacollection. Each of these technologies has different technical characteristics and operatingprinciples, which determine the types of data collected, accuracy of the measurements,levels of maturity, feasibility and cost, and network coverage. This paper reviews the differentsources of traffic surveillance data currently employed, and the types of traffic managementapplications they may support. The current state-of-the-art of traffic modeling is alsodiscussed, in the context of using emerging data sources for better planning, operations anddynamic management of road networks.

  • 36. Antoniou, Constantinos
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Non–linear Kalman Filtering Algorithms for On–line Calibration of Dynamic Traffic Assignment Models2007In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 8, no 4, p. 661-670Article in journal (Refereed)
    Abstract [en]

    An online calibration approach that jointly estimates demand and supply parameters of dynamic traffic assignment (DTA) systems is presented and empirically validated through an extensive application. The problem can be formulated as a nonlinear state-space model. Because of its nonlinear nature, the resulting model cannot be solved by the Kalman filter, and therefore, nonlinear extensions need to be considered. The following three extensions to the Kalman filtering algorithm are presented: 1) the extended Kalman filter (EKF); 2) the limiting EKF (LimEKF); and 3) the unscented Kalman filter. The solution algorithms are applied to the on-line calibration of the state-of-the-art DynaMIT DTA model, and their use is demonstrated in a freeway network in Southampton, U.K. The LimEKF shows accuracy that is comparable to that of the best algorithm but with vastly superior computational performance. The robustness of the approach to varying weather conditions is demonstrated, and practical aspects are discussed.

  • 37. Antoniou, Constantinos
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    On-line Calibration of Traffic Prediction Models2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1934, p. 235-245Article in journal (Refereed)
    Abstract [en]

    A methodology for the on-line calibration of the speed-density relationship is formulated as a flexible state-space model. Applicable solution approaches are discussed and three of them (extended Kalman filter (EKF), iterated EKF, and unscented Kalman filter (UKF) are selected and presented in detail. An application of the methodology with freeway sensor data from two networks in Europe and the U.S. is presented. The improvement in the estimation and prediction of speeds due to on-line calibration (compared with the speeds obtained from the off-line calibrated relationship) is demonstrated. The EKF provides the most straightforward solution to this problem, and indeed achieves considerable improvements in estimation and prediction accuracy. The benefits obtained from the -more computationally expensive-iterated EKF algorithm are shown. An innovative solution technique (the UKF) is also presented. The UKF has a number of unique qualities and advantages over the EKF, including no assumption of analytical representation of the model and no need for explicit computation of derivatives. Empirical results suggest that the UKF outperforms the other two solution techniques in prediction accuracy.

  • 38. Antoniou, Constantinos
    et al.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Estimation of Traffic Dynamics Models with Machine Learning Methods2006In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1965, p. 103-111Article in journal (Refereed)
    Abstract [en]

    Speed-density relationships are a classic way of modeling stationary traffic relationships. Besides offering valuable insight into traffic stream flows, such relationships are widely used in dynamic traffic assignment (DTA) systems. In this research, an alternative paradigm for traffic dynamics models, appropriate for traffic simulation models and based on machine-learning approaches such as k-means clustering, k-nearest-neighborhood classification, and locally weighted regression is proposed. Although these models may not provide as much insight into traffic flow theory as speed-density relationships do, they allow for easy incorporation of additional information to speed estimation and hence may be more appropriate for use in DTA models, especially simulation-based models. This paper (with data from a network in Irvine, California) demonstrates that such machine-learning methods can considerably improve the accuracy of speed estimation.

  • 39.
    Archer, Jeffery
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Indicators for traffic safety assessment and prediction and their application in micro-simulation modelling: a study of urban and suburban intersections2005Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    In order to achieve sustainable long-term transport infrastructure development, there is a growing need for fast, reliable and effective methods to evaluate and predict the impact of traffic safety measures. Recognising this need, and the need for an active traffic safety approach, this thesis focuses on traffic safety assessment and prediction based on the use of safety indicators that measure the spatial and/or temporal proximity of safety critical events. The main advantage of such measures is that they occur more frequently than accidents, and therefore require relatively short periods of study to establish values that can later be used for comparison, or for accident prediction purposes. There are a number of more generally accepted safety indicators including: Time-to-Accident, Time-to-Collision, and Post-Encroachment Time. These are based on different underlying principles and measurement techniques, including both on-site subjective estimation, and objective photometric measures.

    A major part of the work presented in this thesis, concerns identifying the potential and limitations of the different safety indicators with regard to their validity and reliability, and practical use for safety assessment and prediction purposes. This is done in conjunction with field studies in the urban and suburban environment, at both signalised and unsignalised intersections. Results from these studies indicate that on-site observation methods provide useful quantitative and qualitative information relatively quickly and efficiently, provided that they are used correctly. On the other hand, the methods based on photometric measurement (video-analysis) proved arduous and time-consuming. Furthermore, there are questions regarding the abilities of the Time-to-Collision and Post-Encroachment Time safety indicators to adequately represent interaction severity, suggesting possible flaws in fundamental concepts related to construct validity. Importantly, results showed that the relationship between safety indicators and traffic accidents is complex and equivocal, where many different factors and processes can impose a significant influence on safety. This makes generalised predictive modelling a particularly difficult task for safety analysts.

    The potential of micro-simulation for traffic safety and performance estimation based on the use of safety indicators was investigated in the second part of this thesis. Microscopic traffic simulation has become increasingly popular among transport planners, due to the fact that it serves as a safe and flexible off-line test environment for the estimation of dynamic and complex traffic system effects. It is useful and cost-effective in relation to the evaluation of issues concerning roadway design, and technological systems that influence road-user behaviour and vehicle performance. For reasons related to modelling fidelity and data quality, simulation has seldom been used for traffic safety estimation. Simulation model development is however, undergoing rapid development and the area of ‘safety-simulation’ and is recognised as having a high potential in the field of transport planning and traffic engineering.

    As part of the work in this thesis, practical simulation experiments were carried out to investigate this potential, and identify limitations. Based on the data from one of the earlier studies, and knowledge regarding important safety-influencing factors and behavioural processes, one of the simulation experiments showed evidence to suggest that realistic safety critical events could be generated and measured using safety indicators in a simulation environment, without making unnecessary and unrealistic behavioural assumptions. Furthermore, a second application of this methodology revealed the safety potential of a rear-end incident-reduction function used in standard vehicle actuated signalling. While both of these simulation studies highlighted the potential of this type of approach, the need for more flexible and realistic models of interactive behavioural processes could be identified in addition to the general need for greater active research into the field of safety simulation.

  • 40.
    Aronsson, Karin F. M.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Speed characteristics of urban streets based on driver behaviour studies and simulation2006Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    The objective of the study was to gain in-depth knowledge of speed relationships for urban streets. The speed characteristics were examined using a number of methods for data collection. Throughout the research, a special focus was placed on capturing the influence on driver speed of interactions with pedestrians, cyclists and other road users, called sidefriction events in this study.

    First, driver behaviour and travel time data was collected from field and driving simulator studies for a range of street types and traffic conditions. The collected data was used to calibrate a microscopic traffic simulation model. Production runs with this model were performed for various traffic conditions. Second, aggregated speed data was collected at the link level, i.e. the macro level, for three street types. In combination with street site variables, speed and flow data was analysed using multiple regression techniques with space mean speed as dependent variable. This analysis was also performed for average travel speed data produced by microscopic traffic simulation.

    Two central results were attained and utilized for the model development:

    - In-depth knowledge of which factors influence speed choice on urban street links with minor intersections, on a micro and macro level.

    - A comprehensive research methodology for study of speed characteristics on urban streets in which the knowledge gained at the micro and macro level was applied.

    Results from the micro study showed that Average number of crossing pedestrians and Traffic flow had significant impact on average travel speed (R2=0.91). Results from the macro study performed for three street types showed that Street function and Number of lanes also had a high degree of explanation (R2 close to 0.70). The variables Separated bicycle lane, Roadside parking permitted and Number of minor intersections per 1 km were significant for some of the street types modelled in the macro study. The variables Ratio of through vehicles and Gender of the driver were also investigated and were found not to influence space-mean speed. The macro study demonstrated that speed choice and driver behaviour were consistent for each street type investigated regardless of city type and population size. The speed-flow relationships of the micro model for an urban street type showed good agreement with the macro model for traffic flows in the upper range. In conclusion, the research effort showed that the included side-friction variables added explanatory value to the estimation of speed, and thus can enhance the knowledge of traffic impacts of different urban street designs.

  • 41.
    Asplund, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Eriksson, Rickard
    Strand, Niklas
    Price Discrimination in Oligopoly: evidence from regional newspapers2008In: Journal of Industrial Economics, ISSN 0022-1821, E-ISSN 1467-6451, Vol. 56, no 2, p. 333-346Article in journal (Refereed)
    Abstract [en]

    Recent theoretical work has shown that the incentive to target rival firms' customers with low prices can increase price discrimination, and that the strength of the incentive depends on a firm's market position. Using data on Swedish newspaper subscriptions, we find strong support for these predictions. Newspapers with a local competitor sell a larger part of their circulation at a discount than monopoly newspapers. Moreover, in competitive markets, the use of discounts is inversely related to the newspaper's market share. We find no evidence that price discrimination based on observable and exogenous characteristics is influenced by the market structure.

  • 42.
    Asplund, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Economics.
    Friberg, Richard
    Wilander, Fredrik
    Demand and Distance: Evidence on Cross-Border Shopping2007In: Journal of Public Economics, ISSN 0047-2727, E-ISSN 1879-2316, Vol. 91, no 1-2, p. 141-157Article in journal (Refereed)
    Abstract [en]

    An important issue for commodity taxation is the extent to which changes in foreign taxes affect the extent of cross-border shopping and thereby, domestic tax revenue. We use data from Swedish municipalities to estimate how responsive alcohol sales are to foreign prices, and relate the sensitivity to the location's distance to the border. Typical results suggest that the elasticity with respect to the foreign price is around 0.3 in the border region; moving 150 (400) km inland reduces the cross-price elasticity to 0.2 (0.1). Our estimates suggest that a recent Danish cut in the spirits tax reduced Swedish tax revenues from spirits sales by more than 2%, and that an attempt by Sweden to cut taxes in response would reduce tax revenues further.

  • 43.
    Avery, Ryan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Andréasson, Ingmar
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    An Interactive Tool for Collecting Traveler Behavior Information2008Conference paper (Refereed)
  • 44.
    Avery, Ryan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Andréasson, Ingmar
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    An Interactive Tool for Collecting Traveler Behavior Information2008In: Proceedings of the 87th Transportation Research Board Annual Meeting, Jan. 2008, 2008Conference paper (Refereed)
    Abstract [en]

    Understanding driver behavior and response to traffic information is necessary in order toachieve the maximum benefit from Advanced Traveler Information Systems (ATIS). This paperdescribes the development of a travel simulator to collect information on driver route choice inresponse to traffic information. A main feature of the simulator is the realistic representation ofmultiple traffic information sources (currently VMS and radio messages). Furthermore, thesimulator is one of the first Internet-based travel simulators, and the only one that accuratelysimulated the driving task. The simulator consists of collection of pre-trip information anddefault route information followed by multiple simulated trips with varying incidents and trafficinformation. The simulator is evaluated and measures well against established guidelines fortravel simulator development. Results will be discussed in future papers as data collection usingthe simulator is ongoing as of August 2007.

  • 45. Balakrishna, R.
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Time-Dependent Origin-Destination Estimation Without Assignment Matrices2008In: Traffic Simulation, EPFL Press , 2008Conference paper (Refereed)
    Abstract [en]

    Time-dependent origin-destination (OD) flows are crucial inputs to dynamic traffic assignment (DTA) models. However, they are often unobserved, and must be estimated from indirect traffic measurements collected from the study network. Approaches to estimate OD flows from link counts traditionally rely on assignment matrices that map the OD flow variables onto the counts. However, this method (a) approximates the complex relationship between OD flows and counts with a linear function, (b) is restricted to the use of only counts, and cannot exploit richer data such as speeds, densities or travel times, and (c) cannot estimate route choice and supply parameters that critically impact the OD estimates. We present a dynamic OD estimation method that is accurate, flexible in the use of general traffic data, simultaneously estimates all parameters that impact OD estimation, and can be applied to any traffic assignment model.

  • 46. Balakrishna, R
    et al.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Incorporating Within-Day Transitions in Simultaneous Estimation of Dynamic Origin-Destination Flows Without Assignment Matrices2008Conference paper (Refereed)
  • 47. Balakrishna, R
    et al.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Simultaneous Calibration of Dynamic Origin-Destination Matrices with Structural Relationships2008Conference paper (Refereed)
  • 48. Balakrishna, Ramachandran
    et al.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Incorporating Within-Day Transitions in Simultaneous Offline Estimation of Dynamic Origin-Destination Flows Without Assignment Matrices2008In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2085, p. 31-38Article in journal (Refereed)
    Abstract [en]

    An offline methodology is presented: it simultaneously estimates dynamic origin-destination (O-D) matrices, without using assignment matrices that incorporate within-day transition equations. The proposed formulation and solution approach extends a calibration method recently developed that directly uses the output of any network loading model (such as a dynamic traffic assignment or simulation model) so that the complex relationships between O-D flows and model outputs are accurately captured (as opposed to the more common method of approximate linear relationships based oil file assignment matrix). The study extends the original formulation by incorporating spatial and temporal relationships among various O-D flows (transition equations). These transition equations link O-D flow variables across time intervals in such it way that known structural demand patterns can be preserved in the new estimates. Such transition equations, although common in the context of real-time O-D flows, complicate the offline simultaneous estimation of O-D flows and have not been used to their full potential in the past. The approach is demonstrated through a case study.

  • 49.
    Baltzopoulos, Apostolos
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Economics.
    Agglomeration Externalities and Opportunity: Based EntrepreneurshipManuscript (preprint) (Other academic)
  • 50.
    Baltzopoulos, Apostolos
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Essays on High-Quality Entrepreneurship: On the Origins and Survival of Start-ups and the Role of Universities in the Location Decision2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis consists of four self-contained essays on the topic of entrepreneurship.

    [Essay I] uses a unique and detailed Swedish dataset to explore firm, regional, and industry determinants that stimulate spin-offs using the choice of the individuals as the level of analysis. The most important results are that the size of the region and of the local entrepreneurial culture (the relative number of SMEs) has a positive effect on the propensity of the individual to set up a new venture corroborating the results of past firm- and regional-level studies. Industrial specialization is shown to have a positive impact on spin-offs, albeit only in high-tech manufacturing and in knowledge intensive business service sectors. Moreover, using an entropy measure to disentangle unrelated and related variety, it is found that the former has a significantly negative while the latter a significantly positive effect on the propensity of the individual to start a spin-off.

    [Essay II] asks how localisation (MAR) and diversity (Jacobs) externalities affect opportunity-based entrepreneurship across all industry sectors in Sweden’s private economy in the period 1999-2005. MAR externalities are found to positively affect entrepreneurship across all sectors. Jacobs externalities, measured as related variety using an entropy measure, positively affect entrepreneurship in high-tech manufacturing and in knowledge intensive business services but have no significant effect on low-tech manufacturing and other services. The results suggest that previous studies that find no evidence of entrepreneurship benefiting from a diverse local market composition might be using too broad measures of variety.

    [Essay III] analyses how different R&D strategies of incumbent firms affect the quantity and quality of their entrepreneurial spawning. By examining entrepreneurial ventures of ex-employees of firms with different R&D strategies three things emerge: First, firms with persistent R&D investments with a general superiority in sales, exports, productivity, profitability and wages are less likely to generate entrepreneurs than firm with temporary or no R&D investments. Second, start-ups from knowledge intensive business service (KIBS) firms with persistent R&D investments have a significantly increased probability of survival.  No corresponding association between the R&D strategies of incumbents and survival of entrepreneurial spawns is found for incumbents in manufacturing sectors. Third, spin-outs from KIBS-firms are more likely to survive if they start in the same firm, indicating the importance of inherited related knowledge. The findings suggest that R&D intensive firms spur fewer entrepreneurs, but their entrepreneurial spawns tend to be of higher quality.

    [Essay IV] investigates how universities may affect regional entrepreneurship through the localisation decisions of entrepreneurial alumni. Empirically, a comprehensive, individual-level dataset from Sweden is used for the period 2003-2005. The results suggest that even when controlling for their spatial history, individuals have an increased propensity to set up in the region where they studied. This effect is found to substitute for both urbanisation economies and localisation economies as drivers of regional-level entrepreneurship. Thus, the analysis provides evidence on how universities affect regional economic development that complements the strong focus on spin-off activities by university researchers in previous studies.

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