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Abstract: This paper discusses a number of issues relating to the pre-analysis and cleaning of stated choice data, where we look specifically at the problems caused by non-trading, lexicographic and inconsistent response patterns. We argue that this process is considerably more complex and challenging than many in the field have hitherto acknowledged, with the standard practice being the use of rather ad hoc procedures for the identification of these phenomena. A detailed analysis on four different stated choice datasets highlights the potential impacts of these methods on model estimation results. [Copyright &y& Elsevier]

There are nearly two million subscribers to carsharing services worldwide. These services can provide large benefits both to users and the general public (e.g., through emissions reductions). There has not however previously existed a general framework for forecasting their market potential and impacts that is sensitive to the way that they re-structure the costs associated with personal car ownership. Techniques for predicting market scope and impacts ahead of field implementation are urgently required, both by entrepreneurs and the public sector, whose support, or at least acquiescence, is generally required. This paper draws on the Perceived Activity Set conceptual framework that was recently developed to address the methodological challenges posed by carsharing, and presents the first set of empirical findings from employing it to model carsharing. The empirical analysis makes uses of pooled data from the British National Travel Survey and a purpose-designed stated-choice survey. We investigate both the ‘round-trip’ and ‘point-to-point’ carsharing service models. The results suggest that the number of prospective subscribers to a point-to-point carsharing service in London is between three and four times as large as the comparable number for round-trip carsharing. The greatest reduction in overall vehicle-miles of travel – including both carsharing cars and private cars – was found from introducing round-trip carsharing across all of London. Survey respondents indicated they would use point-to-point carsharing for commuting journeys much more frequently than round-trip carsharing. Finally, point-to-point carsharing was found to be a substitute for public transport, whilst round-trip carsharing was found to be a complement. [ABSTRACT FROM AUTHOR]

Abstract: Emissions from motor vehicles are a major source of air pollution and studies have shown that exposure to the particulate matter in fresh diesel exhaust is a significant risk to health. Short-term peak exposures are thought to have the greatest impact. Despite the development of several vehicle power-based models to estimate the second-by-second mass emission rates of gaseous pollutant species such as carbon monoxide, carbon dioxide, hydrocarbons and nitrogen oxides, none of these models predicts particulate matter emissions. This paper presents a new technique for modelling the second-by-second particulate matter mass emission rate of a light-duty diesel vehicle. Here, particulate matter emission rates are modelled as a function of both vehicle kinematic parameters (i.e., speed or acceleration) and the mass emission rates of the gaseous co-pollutants. The importance of time alignment in the calibration data is evaluated and a technique for deriving an appropriate lag structure is devised. Various regression models are estimated that provide a good model fit, comparable to existing models of gaseous pollutants. [Copyright &y& Elsevier]