Testing the Importance of Fixing Exogenously Some Parameters in Aggregate Modal Split Models, by means of Sensitivity Analysis.

Aggregate modal split (and distribution) models currently need exogenously determined values for such key parameters as the value of in-vehicle time, the value of waiting time and the car occupancy factor. Using hierarchical logit modal split models and data from the Garforth Corridor, to the east of Leeds, this paper set out to investigate the effects in the model aggrement to the data (and hence in its forecasting capabilities) of inputting different values for these parameters. 'To gain insight into the relative importance of each of these fixed parameters,the analytical point elasticities of the free parameters in the model with respect to them, were briefly examined. This exercise, together with some more practical post-hoc considerations led us to concentrate on the values of in-vehicle time and waiting time only. The rather surprising outcome of the analysis was that the model fits were not statistically different, for different values of the fixed parameters, their variation being accommodated by changes in the values of the free parameters. The main conclusion was that provided the exogeneous parameters are reasonably accurate they should produce models that are capable of performing as well (or badly) as models calibrated entirely from the data, and at a much lower cost

Assessing the Value of Time Travel Savings – A Feasibility Study on Humberside.

It is expected that the opening of the Humber Bridge will cause major changes to travel patterns around Humberside; given the level of tolls as currently stated, many travellers will face decisions involving a trade-off between travel time, money outlay on tolls or fares and money outlay on private vehicle running costs; this either in the context of destination choice, mode choice or route choice. This report sets out the conclusions of a preliminary study of the feasibility of inferring values of travel time savings from observations made on the outcomes of these decisions. Methods based on aggregate data of destination choice are found t o be inefficient; a disaggregate mode choice study i s recommended, subject to caveats on sample size

Testing the Theoretical Accuracy of Travel Choice Models Using Monte Carlo Simulation.

In recent years a considerable advance has been made in the construction of micro-travel demand models from choice theoretic principles. Within random utility theory, the structure of models may be shown to relate to the perceived similarity between discrete choice alternatives, and this aspect may be interpreted mathematically in terms of the correlation between the components of random utility functions. Several possible model structures have now been proposed, varying from the multinomial logit model (uncorrelated) through the partly correlated structures (hierarchical and cross-correlated logit kctions) to the most general form of probit model which allows an arbitrary variance-covariance matrix. In this paper, these model structures are discussed using a geometric interpretation of random utility theory, and the possibility of invoking transformations on the general probit model is examined. Monte Carlo simulation methods are then used to investigate some aspects of the trade-off between the generality and accuracy of correlated structures (the cross-correlated logit model in particular) and the greater ease with which less consistent structures may be implemented. In this way, the theoretical accuracy of the multinomial logit model is assessed. It is concluded that where the general probit model is too complex to implement, the practice of comparing the multinomial logit model with alternative hierarchical logit structures is unlikely to lead to significant errors in forecasting

On fitting mode specific constants in the presence of new options in rp/sp models

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Risk Assessment and Research Synthesis methodologies in food safety: two effective tools to provide scientific evidence into the Decision Making Process.

The food supply chain is a complex and diverse system. Some food products need minimum processing to reach the consumers, while others involve several different processes, countries and suppliers, can take several months to be on the table of the end consumer. Regarding food safety, the public health of consumers is at stake and the consequences of outbreaks could prove disastrous. This has been recognized as a matter of global importance for the food industry and authorities around the world since several efforts to improve quality, safety and trade of food have arisen since the early 1960s. The birth of the Codex Alimentarius Commission, a joint organism lead by the World Health Organization and the Food and Agriculture Organization, marks a milestone, creating the first organization dedicated to proposing international food safety standards and to foster fair global food trade. All these organizations agree that the use of solid scientific evidence in the decision making process is the cornerstone in creating a safe global food supply chain. Although there is widespread consensus about this, developing countries usually encounter heavy difficulties in accomplishing these objectives due to obstacles such as low funding to sample their food products, a weak regulatory system, insufficient technology and scientific capabilities. Therefore, addressing the question “how can we provide tools for these countries to strengthen their capacities to create scientific evidence based regulations with the consideration of these limitations?” is in great need. In this project two case studies were used to show that risk assessment, in conjunction with the use of research synthesis methodologies, are two approaches that can be used by the food industry and governments to provide effective scientific insights into their respective decision making processes. The focus of this research project is food safety in Chile, thus the analysis, results and overall direction will be narrowed to the perspective of this developing country. Advisors: Bing Wang and John Rupno

Risk Assessment and Research Synthesis methodologies in food safety: two effective tools to provide scientific evidence into the Decision Making Process.

The food supply chain is a complex and diverse system. Some food products need minimum processing to reach the consumers, while others involve several different processes, countries and suppliers, can take several months to be on the table of the end consumer. Regarding food safety, the public health of consumers is at stake and the consequences of outbreaks could prove disastrous. This has been recognized as a matter of global importance for the food industry and authorities around the world since several efforts to improve quality, safety and trade of food have arisen since the early 1960s. The birth of the Codex Alimentarius Commission, a joint organism lead by the World Health Organization and the Food and Agriculture Organization, marks a milestone, creating the first organization dedicated to proposing international food safety standards and to foster fair global food trade. All these organizations agree that the use of solid scientific evidence in the decision making process is the cornerstone in creating a safe global food supply chain. Although there is widespread consensus about this, developing countries usually encounter heavy difficulties in accomplishing these objectives due to obstacles such as low funding to sample their food products, a weak regulatory system, insufficient technology and scientific capabilities. Therefore, addressing the question “how can we provide tools for these countries to strengthen their capacities to create scientific evidence based regulations with the consideration of these limitations?” is in great need. In this project two case studies were used to show that risk assessment, in conjunction with the use of research synthesis methodologies, are two approaches that can be used by the food industry and governments to provide effective scientific insights into their respective decision making processes. The focus of this research project is food safety in Chile, thus the analysis, results and overall direction will be narrowed to the perspective of this developing country. Advisors: Bing Wang and John Rupno

Multimodal Choice Modelling – Some Relevant Issues.

This paper gives an overview of the most relevant issues relating to the application of multimodal choice models ranging from data considerations, such as alternative sampling strategies and measurement techniques, to the hotly debated aggregation issue. Particular emphasis is placed on the specification and estimation problems of disaggregate choice models

Macroeconomic impacts of water allocation under droughts. Accounting for global supply chains in a multiregional context

Water allocation policies play a key role in determining the impact of drought events on the macroeconomic system. Economic agents may find it difficult to modify their production structure immediately, and will therefore try to maintain current production and commercial patterns. The study takes this behavior into account and combines a Multi-Regional Input-Output model with a Non-Linear Programming optimization model to assess the macroeconomic impacts of localized droughts on a global scale. It analyses their propagation through interconnected supply chains, and it also evaluates the implications of different water allocation policies in terms of GDP impacts, with a large regional and sectoral detail. Our results show that the policy-regime chosen greatly determines the extent of the economic impacts, both in the directly affected region and in third countries. When the drought affects only agriculture, that negative economic impacts can be mitigated by adjusting production and trade. In contrast, when water availability is reduced uniformly across all economic sectors in the drought-stricken region, economic losses spread across the globe

Valuing Noise Level Reductions in a Residential Location Context

The noise levels measured in metropolitan streets are on many occasions over the norms but the consequences of this as a health hazard are only starting to be questioned; this is obviously worse in the large cities of the second and third worlds. A stated preference (SP) experiment was designed to estimate the willingness-to-pay (WTP) for reducing the noise level in a group based residential location context. Important issues were the proper definition of the context and the variable metric for the environmental attribute. The experiment considered variations of the attributes travel time to work, monthly house rent, position of the dwelling with respect to the sun and subjective noise level inside it; objective levels were also measured after the experiment. With this data we estimated Multinomial Logit and Mixed Logit (ML) models based on a consistent microeconomic framework, with linear and non-linear utility functions and allowing for various stratifications of the data. The more flexible ML models also allow to treat the repeated observations problem common to SP data and, as expected, gave a better fit to the data. Based on these models we estimated subjective values of time, that were consistent with previous values obtained in the country, and also sensible values for the WTP for reductions in the subjective noise level at a given location

Razvoj avtonomnih učnih načrtov in učbenikov v španskem osnovnošolskem izobraževanju - geografska analiza

Evolution by natural selection is a theory that constitutes a powerful paradigm capable of conveying the teaching-learning of multiple concepts in biology. However, it has been controversial from its formulation to the present, which also affects education. For instance, while some of the basic curricula of primary education in Europe are arranged around the concepts that are considered necessary for structuring the scientific model of evolution (i.e., Sweden), other curricula do not contemplate such concepts. The last is the case of the basic curriculum of primary education in Spain. However, in Spain, on the basis of such a curriculum, there are 17 different primary education curricula corresponding to each of the autonomous communities of the state. The objective of this work is to state a detailed geographical picture of the presence of the concepts necessary to articulate the model of evolution through the analysis of the autonomic curricula of Spain. With such an aim, words that represent such concepts (evolution, inheritance, selection, adaptation and biodiversity, etc.) have been searched for in the natural sciences and social sciences areas of the autonomous curricula of primary education. Furthermore, a search for such evolution-related concepts has also been performed in the activities of eighteen Spanish primary education textbooks on natural and social science subjects. For this purpose, two aspects were considered: characterisation and scientific skills. Both the autonomous curricula of primary education and the textbooks hold important gaps when addressing evolution. The texts include activities that prioritise basic cognitive skills over the more demanding ones associated with scientific competence. (DIPF/Orig.