Highlights-Extensive range of environmental impacts is rarely considered in decision analysis.-LCA can provide sophisticated environmental profiles of decision alternatives.-LCA and other decision analysis tools have different goals, principles and systems.-Consistency of study system between LCA and other tools is the key for integration.
Uncertainty is inherent to transport models and prevents from using a deterministic approach when modelling traffic. Quantifying uncertainty thus becomes an indispensable step to produce more informative and reliable output of transport models. Within traffic assignment models, volume delay functions express the travel time as a function of traffic flows and theoretical capacity of the modelled facility. The US Bureau of Public Roads (BPR) formula is one of the most extensively applied volume delay functions in practice. This study investigated uncertainty in the BPR parameters. Initially, BPR parameters were estimated by analyzing observed traffic data related to the Danish highway network. Then, BPR parameter distributions were generated by using re-sampling Bootstrap technique. Finally, the generated parameter vectors were used to implement sensitivity tests on the four-stage Danish national transport model. The results clearly highlight the importance for modelling purposes of taking into account BPR formula parameter uncertainty, expressed as a distribution of values rather than assumed point values. Indeed, the model output demonstrates a noticeable sensitivity to parameter uncertainty. This is particularly evident for stretches of the network with a high number of competing routes. Model sensitivity was also tested for BPR parameter uncertainty combined with link capacity uncertainty. The resulting increase in model sensitivity demonstrates even further the importance of the implementation of uncertainty analysis as part of a robust transport modelling process.
Transport cost-benefit analysis frameworks do not consider the environmental impacts deriving from the life cycle of the transport system’s components. This leads to an inaccurate representation of the environmental impacts of transport projects, which can be instead more thoroughly represented by life cycle assessment methods. In the present study, we describe a transport cost-benefit analysis model combined with a life cycle assessment module developed based on life cycle ReCiPe 2016 methodology. The suggested approach makes it possible to include the life cycle impacts on human health, ecosystem and natural resource depletion in the project assessment. We discuss the methodological issues of combining cost-benefit analysis and life cycle assessment in transport appraisals. We illustrate the results from the application of the model to a transport case study related to the construction of a new fixed link across the Roskilde Fjord in Frederikssund (Denmark). The analysis shows that the environmental impacts deriving from the life cycle of the system components notably affect the key indicators of the model output, such as benefit-cost ratio and net present value. The results from the model are then tested through sensitivity analysis related to some of the assumptions made for the study. The study concludes that the inclusion of life cycle impacts in transport cost-benefit frameworks allows taking into account environmental costs and benefits otherwise not accounted for, thereby providing to the decision makers a more exhaustive information about the environmental impacts of the project.
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