A simultaneous two-dimensionally constraint disaggregate trip generation, distribution and mode choice model - Theory and application for a Swiss national model

The Swiss federal government has asked the IVT, ETH Zürich in collaboration with the TU Dresden and Emch+Berger, Zürich to estimate origin-destination matrices by mode and purpose for the year 2000. The zoning system employing about 3’000 zones of very uneven size required a solution algorithm which is fast, but also able to model generation, distribution and mode choice simultaneously, while addressing the different data availability for traffic within, destined for and passing through the country. The EVA algorithm developed by Lohse (1997) was adapted for this purpose. The key proper-ties of the algorithm are its disaggregate description of demand, its use of appropriate logit-type models for the demand distribution, while maintaining the known marginal distributions of the matrices generated. This last point is of particular importance in a large scale planning applica-tion such as the one at hand. The algorithm calculates trip production and attractions by zone using activity pairs. The 17 ac-tivity pairs distinguished are the combinations of two activities, such as home-work or work-leisure. The relevant daily rates are derived for each of the 17 activity pairs from the 2000 Swiss National Travel Survey (Bundesamt für Statistik and Bundesamt für Raumentwicklung, 2001). The zonal attractivity is defined separately for each trip purpose. In addition to the common variables, such as employment or population, detailed descriptions of education places, shop-ping or leisure facilities, overnight accommodations, shopping centres etc. are employed (see Tschopp, Keller and Axhausen, 2003 for the data). The combined destination and mode choice models estimated for the different traveller types and activity pairs are based on the Swiss National Travel survey (RP data), but incorporates re-sults from a prior SP study on mode and route choice (Vrtic and Axhausen, 2004). The different zone sizes and the different levels of data available required the formulation of new additional models for the transit traffic passing through Switzerland and the traffic originat-ing outside, respectively leaving the country The matching network models for public transport and road traffic were implemented using VISUM 9.0 of PTV AG, Karlsruhe. The timetable based assignment considers all scheduled train services plus the relevant interurban bus services, in particular in rural areas. The paper has three main parts: the first main part derives and describes for the first time the EVA algorithm in English, including the solution method used. The second part summarizes the results of choice model estimation using the generalised cost elasticities of demand by purpose and traveller type. The third part assesses the quality of the results. These assessments are based on two independently derived matrices, which are available for rail-travel from on board - counts and for commuters from the 2000 national census. In addition, we compare the assign-ment results with the available cross section counts. The conclusions discuss computing times, accuracy and issues for further research.

Reconstructing the 2003/2004 H3N2 influenza epidemic in Switzerland with a spatially explicit, individual-based model

ABSTRACT: BACKGROUND: Simulation models of influenza spread play an important role for pandemic preparedness. However, as the world has not faced a severe pandemic for decades, except the rather mild H1N1 one in 2009, pandemic influenza models are inherently hypothetical and validation is, thus, difficult. We aim at reconstructing a recent seasonal influenza epidemic that occurred in Switzerland and deem this to be a promising validation strategy for models of influenza spread. METHODS: We present a spatially explicit, individual-based simulation model of influenza spread. The simulation model bases upon (i) simulated human travel data, (ii) data on human contact patterns and (iii) empirical knowledge on the epidemiology of influenza. For model validation we compare the simulation outcomes with empirical knowledge regarding (i) the shape of the epidemic curve, overall infection rate and reproduction number, (ii) age-dependent infection rates and time of infection, (iii) spatial patterns. RESULTS: The simulation model is capable of reproducing the shape of the 2003/2004 H3N2 epidemic curve of Switzerland and generates an overall infection rate (14.9 percent) and reproduction numbers (between 1.2 and 1.3), which are realistic for seasonal influenza epidemics. Age and spatial patterns observed in empirical data are also reflected by the model: Highest infection rates are in children between 5 and 14 and the disease spreads along the main transport axes from west to east. CONCLUSIONS: We show that finding evidence for the validity of simulation models of influenza spread by challenging them with seasonal influenza outbreak data is possible and promising. Simulation models for pandemic spread gain more credibility if they are able to reproduce seasonal influenza outbreaks. For more robust modelling of seasonal influenza, serological data complementing sentinel information would be beneficia

Legislative Documents

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Simultanes Routen- und Verkehrsmittelwahlmodell

Bei verkehrspolitischen und infrastrukturellen Massnahmen folgen als wesentliche Nachfrageveränderungen vor allem Routen- und Verkehrsmittelwahleffekte. Mit der Anwendung der sequentiellen Routen- und Verkehrsmittelwahlmodelle, ist bei solchen Massnahmen aus verschiedenen Gründen eine konsistente und gesamthafte Gleichgewichtslösung nicht möglich. Das Ziel dieser Untersuchung war, ein konsistentes und verfeinertes Verfahren zu entwickeln, mit dem die Routen- und Verkehrsmittelwahl simultan bzw. in einem Schritt als eine Entscheidung berechnet werden kann. Neben dem Gleichgewicht bei der Verteilung der Verkehrsnachfrage auf die Alternativen, war die konsistente Schätzung der Modellparameter für die Bewertung von Einflussfaktoren bei den Entscheidungen hier eine weitere wichtige Anforderung. Das Modell ist in der Lage, ein realitätsentsprechendes Verhalten der Verkehrsteilnehmer, sowohl bei schwach, als auch bei stark belasteten Strassennetzen, zu beschreiben. Die unterschiedliche Wahrnehmung der Reisekosten der Verkehrsteilnehmer und die Netzüberbelastungen werden durch ein stochastisches Nutzergleichgewicht abgebildet. Das entwickelte Verfahren ermöglicht es: - die Nachfrageaufteilung mit einem konsistenten Gleichgewicht zwischen Verkehrsangebot und Verkehrsnachfrage zu berechnen. Dabei wird ein Gleichgewicht nicht nur innerhalb des Strassen- oder Schienennetzes, sondern zwischen allen verfügbaren Alternativen (unabhängig vom Verkehrsmittel) gesucht. - durch die iterative Kalibration der Modellparameter und die Nachfrageaufteilung ein konsistentes Gleichgewicht zwischen den geschätzten Modellparametern für die Nutzenfunktion und der Nachfrageaufteilung auf die vorhandenen Alternativen (Routen) zu berechnen. - mit einem stochastischen Nutzergleichgwicht die unterschiedliche Wahrnehmung der Nutzen bzw. der generalisierten Kosten der Verkehrsteilnehmer bei der Nachfrageaufteilung zu berücksichtigen. - die Auswirkungen von Angebotsveränderungen auf die Verkehrsmittelwahl und Routenwahl durch simultane Modellierung der Entscheidungen konsistent und ohne Rückkoppelungschritte zu berechnen