TRANSIMS is a disaggregate, behavioral transportation planning package developed under US DOT's and EPA funding at the Los Alamos National Laboratory (LANL). It is an integrated system of travel forecasting models designed to give transportation planners accurate, complete information on traffic impacts, congestion, and pollution by simulating second-by-second movements of every person and every vehicle through the transportation network of a large metropolitan area. There is no built-in module for travellers' mode choices In TRANSIMS. The modes going with the shortest path are always taken. In Portland Study, a mode choice methodology implemented by a series of feedback processes is proposed. However, it uses aggregate, deterministic mode choice model. There is little solid theoretic ground for the format and coefficients of the generalized costs used in the calibration process. The accessibility to a mode, especially to Transit, was also not included in the model. In the thesis, a disaggregate and deterministic mode choice methodology in TRANSIMS is developed. The accessibility to each mode is analyzed and included in the model. The methodology is then implemented on the Blacksburg transportation planning study, namely Blacksburg_Lite. The analysis of the result is based on the indicator of mode choice, mode split between Transit and Auto. The indicator is close to that in survey data and converged fast. Therefore, this mode choice methodology could be used within TRANSIMS framework. / Master of Science

Cette thèse a proposé quelques développements pour améliorer la modélisation appliquée de la mobilité liée à l'activité d'achat de la population d'une agglomération. Pour ce faire, nous nous sommes appuyés sur un schéma de principe du processus de caractérisation de cette mobilité. Dans ce schéma nous avons considéré que cette mobilité est définie au sein d'un ménage en répondant à quatre questions posées simultanément (qui ?, où ?, comment ? et quoi ?). La première partie de cette thèse porte sur les aspects tant qualitatifs que quantitatifs qui doivent apparaître dans le schéma ; la deuxième, sur les outils de modélisation théorique et opérationnelle ; la troisième, sur la construction du schéma proprement dit ; et la quatrième, sur l'utilisation appliquée d'un outil déjà existant. Les contributions principales de notre thèse consistent en l'utilisation d'une approche systémique pour décrire cette mobilité et l'utilisation de techniques peu utilisées actuellement en France / This thesis has aimed to enhance some aspects of the modelling of shopping trips in an urban area. We have used a block diagram to represent the mechanisms used to define this mobility and we have focused on some sides of this problem in a disaggregated approach. In our diagram we have supposed that shopping trips are defined in a household by answering four simultaneous questions (who?, where?, how? and what?). We have started by studying the qualitative and quantitative elements which must appear in our block diagram and we have continued by the study of the existing theoretical and applied modelling tools. We could then build our block diagram, and we have finished by using an existing modelling tool. The main contributions of our work are the use of a systemic approach for the description of this mobility and the use of techniques not common in France

In this study, exchange rate pass-through into the export prices and import prices is analyzed separately at the disaggregate level. The study also attempts to differentiate exchange rate pass-through in the short-run and long-run. To analyze pass-through in the short-run, dynamic modeling is used. To analyze pass-through in the long-run, cointegration analysis is conducted. Estimation results show that exchange rate pass-through into the import prices is complete even at the disaggregate level. However, there is variation in the pass-through into the export prices across sectors both in the short-run and long-run. Not all exporting sectors, even in a small open economy like Turkey, are price takers in the foreign markets.

Freight demand models have not been developed that much as passenger demand models. The reason is existence of too many complexities in this area. To estimate a disaggregate freight transport models large input data is required. The Swedish Flow Commodity survey 2004/2005 (CFS) which is a unique data source at the level of individual firms made it possible to estimate a disaggregate model to analyze the choice of transport chains and shipment size for the domestic metal products. The output of logistics module of the Swedish national freight transport (SAMGODS) is used as an auxiliary database to incorporate logistics decisions which CFS lacks in the model. The model comprises logistics perspective by considering both shipment size and transport chains as endogenous choices. Characteristics of shippers, shipments and transport chains are included in the model to analyze the choice of transport chain and shipment size. It has been tried to include as many transport chains as possible in the choice sets to consider their effects on decision making. Transport costs have been included in the model as shipment size specific to incorporate the concept of logistics more precisely in the model. From the results it can be seen that the freight transport demand is almost inelastic to the cost. The model gives a positive sign for the coefficient of the transport time which can be explained as the storage cost is so high that shippers prefer to use transport modes as the moving inventories instead. Finally, it is suggested to estimate panel discrete choice models on this dataset.

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Excessive sedimentation is a leading cause of aquatic life use impairments in Virginia. As required by the Clean Water Act, a total maximum daily load (TMDL) must be developed for impaired waters. When developing a TMDL for aquatic life use impairment where sediment has been identified as the primary pollutant, the target sediment load is often determined using a non-impaired reference watershed, i.e., the reference watershed approach (RWA). The RWA has historically been used in Virginia to establish TMDL target sediment loads because there is no numeric ambient water quality criterion for sediment. The difference between the sediment load generated by the reference watershed and the load generated by the impaired watershed is used to determine the sediment load reduction required to meet the TMDL target load in the impaired watershed. Recent quantification of the Chesapeake Bay TMDL based on Phase 5.3 of the Chesapeake Bay Watershed Model (CBWM) offers a simpler and potentially more consistent method of calculating target sediment loads for impaired watersheds within the Chesapeake Bay watershed. Researchers in the Biological Systems Engineering department at Virginia Tech have developed the "disaggregate method" (DM) which uses landuse inputs to, and pollutant load outputs from, the CBWM to determine pollutant load reductions needed in watersheds whose areas are smaller than the smallest modeling segments generally used in the CBWM. The DM uses landuse-specific unit area loads from two CBWM model runs (an existing condition run and TMDL target load run) and a finer-scale, locally assessed landuse inventory to determine sediment loads. The DM is simpler and potential more consistent than the reference watershed approach. This study compared the reference watershed approach and the disaggregate method in terms of required sediment load reduction. Three sediment-impaired watersheds (Long Meadow Run, Taylor Creek and Turley Creek) within the Chesapeake Bay watershed were used for the study. Study results showed that the TMDL development method used to determine sediment loads would have noticeable effects on resulting sediment-load reduction requirements. For Taylor Creek, the RWA required 20.4 times greater reductions in sediment load (tons/yr) when compared to the DM. The RWA also required 9.2 and 10.4 times greater reductions for Turley Creek and Long Meadow Run watersheds, respectively. On a percentage basis, the RWA for reduction Taylor Creek was 7.3 times greater than that called for by the DM. The RWA called for 4.4 and 4.6 times greater percent reductions for Turley Creek and Long Meadow Run watersheds, respectively. An ancillary objective of this research was to compare the sediment load reductions required for the impaired and their respective RWA-reference watersheds, using the DM. This comparison revealed that, both Taylor Creek and Turley Creek watersheds required less sediment load reduction than their respective reference watersheds, while the load reductions required for Long Meadow Run were slightly greater than its reference watershed. There are several issues associated with either the RWA or the DM for developing sediment TMDLs. Those issues are discussed in detail. Recommendations the need for further studies, based in questions raised by the research presented here are also discussed. / Master of Science

This dissertation consists of three essays. In the first essay, econometric models are used to measure price risk in a study for major grains (wheat, rice, corn, and soybeans) in China. Generalized Autoregressive Conditional Heteroskedasticity (GARCH) models and Multiplicative Heteroskedasticity (M Het) models are applied to estimate time-varying price variance, and then covariances are estimated by a simple two-step process assuming constant conditional correlations. An aggregate price risk index is constructed from these variances and covariances using an economic index number approach. In theory, this approach is superior to the more common approach of estimating a univariate GARCH model for an aggregate price index. This easay compares the two approaches to measuring aggregate price risk and finds low correlations. Thus there is substantial difference between the two approaches in practice as well as in theory. The previous essay measures aggregate price risk but does not explain price risk. The second essay attempts to investigate potential factors that contribute to aggregate price risk of major grain products (rice, wheat, corn and soybeans) on monthly base in China from mid 1980s to recent year from both theoretical and empirical perspectives. The superlative price risk indexes are explained by a set of key variables that characterize China’s economy, agricultural market and trade as well as biological system of major grain in China. These variables account for much of the variation in the aggregate price risk index. Moreover empirical results favor use of the superlative index of aggregate risk rather than standard measures of aggregate risk. The third essay is an extension of previous two essays by explaining price risk at disaggregate level. Price variances and covariances are modeled using both Ordinary Least Squares (OLS) and Seemly Unrelated Regression (SUR) techniques. Results are broadly consistent with the previous essays.

Minimum Concave Cost Multicommodity Network Design Problem arises in many application areas, such as transportation planning, distributed energy system and especially both circuit and packet switching backbone network design. Exact concave optimization algorithms have been developed, but these methods are applicable if the network size is small. Therefore, these problems are usually solved by non-exact iterative methods. In this thesis work, methods proposed for circuit switching and packet switching network design are evaluated in detail. After a comprehensive literate survey, Yaged&rsquo / s Linearization, Minoux greedy and Minoux accelerated greedy methods are found to be applicable to circuit switching network design when both solution quality and computational time is considered. Previously, it has been found that Minoux greedy methods may create routings with cycles and in order to eliminate these cycles a modification has been proposed. In this work, this modification is extended and evaluated in detail. Similarly, Gerla and Kleinrock&rsquo / s Concave Branch Elimination, Gersht&rsquo / s greedy and Stacey&rsquo / s Concave Link Elimination methods are investigated within the context of packet switching network design. All of these methods consider aggregate flows on each link simultaneously re-routing more than one commodity in one step. This thesis work also considers an alternative disaggregate approach, where only one commodity is handled at a time. Finally, algorithms proposed for circuit switching network design problem are adapted to the packet switching case and an extensive comparative computational study is performed to point out the best method with respect to time and solution quality for a number of networks and cost structure. Computational results have shown that modification on Minoux greedy to eliminate cycles leads to considerable improvements and the disaggregate approach gives the best result in some networks and cost structure.

Transport models are key in predicting travel behaviour and planning transport systems. Transport models can be either aggregated or disaggregated. Disaggregation means that travel behaviour is represented on an individual level, which can be beneficial because it offers a higher detail level and reduces aggregation bias. Input data for transport models can be both expensive and inaccessible, especially comprehensive data. Thus, it is advantageous to explore the utilisation of open data, which is free and accessible. The objective of the thesis was to evaluate how OpenStreetMap and other Open Data can be utilised in disaggregated transport modelling. The scope of the study was Uppsala, Sweden. In the thesis, a disaggregate transport model was designed, which only considered commuting trips made by public transport. Destinations and a synthetic population were estimated based on OpenStreetMap map features, SCB census data, and LuTRANS land use data. A travel survey was utilised in model calibration, and UL boarding data was used for model validation. The results showed that OpenStreetMap provided sufficient data for estimating a synthetic population and destinations for a disaggregate transport model when combined with other open data sources. Population and land usecensus data were essential for calibrating the model. However, the model came with limitations caused by assumptions, generalisation, technical constraints, and the partial incompleteness of open data. The thesis concludes that Open Data, such as OpenStreetMap, can be utilised sufficiently for transport modelling, with proper assumptions and processing. The openness of the data also increases the replicability of such a model. / Transportmodeller är viktiga i att förutspå resvanemönster och för att kunna planera transportsystemet. Transportmodeller kan vara antingen aggregeradeeller disaggregerade. Disaggregering betyder att resvanor är representerade påindividuell nivå, vilket kan vara fördelaktigt då det innebär en högre detalj nivå och mindre partiskhet orsakad av aggregering (aggregation bias). Indata förtransportmodeller kan vara både dyrt och svåråtkomligt, speciellt för mer omfattande data. Därav kan det vara till stor nytta att utforska möjligheten att använda öppnadata (Open Data), som är gratis och lättåtkomligt. Syftet med examensarbetetvar att utvärdera hur OpenStreetMap och annan Open Data kan användas idisaggregerad transportmodellering. Den geografiska omfattningen av studien är Uppsala tätort. En disaggregerad transportmodell togs fram i examensarbetet, sombara tog hänsyn till jobbresor med kollektivtrafik. Destinationer och en syntetiskbefolkning uppskattades utifrån OpenStreetMap objekt, befolkningsdata från SCB, samt markanvändningsdata från LuTRANS. En resvaneundersökning utnyttjadesför modellkalibrering och påstigningsdata från UL användes för modellvalidering.Resultaten visade att OpenStreetMap erbjöd tillräckligt med data för att ta framoch uppskatta en syntetisk befolkning och destinationer för en disaggregeradtransportmodell, om den kombineras med andra öppna datakällor. Befolkning- ochmarkanvändningsdata var avgörande i att kalibrera modellen. Dock så innefattar modellen vissa begränsningar som är orsakada av antaganden, generalisering, tekniskabegränsningar, samt ofullständigheten av Open Data. Slutsatsen är att Open Data, så som OpenStreetMap, kan utnyttjas för transportmodellering, om det kombineras med välformulerade antaganden och processering av datan. Datans öppenheten medför även en ökad replikerbarhet för en sådan modell.

No description available.