The Ørestad Traffic Model (OTM) is a well-established model for the Greater Copenhagen Area. It is currently in the process of being revalidated with updated TU data, i.e. the new 2004 base tour matrices will be built andthe demand model will be re-estimated. A parallel modelling process is inplace to estimate an activity-based model called Copenhagen Model for Passenger Activity Scheduling (COMPAS). The process will lead to a gradual transition from OTM to COMPAS. The planning reasons for shifting to COMPAS are: better understanding of consequences of introducing road pricing in Copenhagen as well as congestion problems on the access roads to the city. The tour generation model components will be the first to be estimated and the first COMPAS model components to replace the OTM model components. Thus, this paper will focus on comparing the tour generation models between aconventional and activity-based approach. A pure comparison between the two types of models is not meaningful, since activity-based models are structured differently. Activity-based models are typically tour-based and have far fewer non-home based tours than conventional models (the majority ofwhich are trip based). In many instances, we need a methodology to compare total tours out of an activity-based model to the trips out of a conventional model and perhaps more importantly to compare total passenger miles by mode. Of course, the comparison is more direct if the conventional model is tour-based. OTM is a tour-based model, which does assist us in makingcomparisons between the models. Nonetheless, it is still possible that tours are categorized or defined differently. For instance, many activity-based models have an explicit escorting purpose, which would more typically be grouped together with other maintenance tours in a conventional, tour-based model. Thus, the raw number of tours by different purposes will probably not coincide completely between models. Important comparisons that canbe made between the models are looking at the sensitivities of travellersto changes in time and cost. If these differ between models and they might, the modeller needs to be able to explain how the structures of the model influence these values. This paper will set out a number of structural differences between OTM and COMPAS and track through the model how these differences affect estimation results. The other important comparison that should be made between models is to show how they can be used to inform policy makers. In general, this is considered a strength of activity-based models, since they are more behaviourally detailed. Activity-based models are built upon a better understanding of intra-household interactions and interdependencies that lead to joint activities and travel. In practical terms, the joint travel feature which can be built into activity-based modelsis critical for proper modelling of congestion pricing schemes. The nature of activity-based models also allows for more detailed investigations ofpolicy options, such as varying parking charges by time of day. However, one major issue is that policy makers have come to expect certain output from travel models. They may not be equipped to incorporate new kinds of information or the information they seek may not be easily extracted from the model output. The final comparison between OTM and COMPAS will be to evaluate its ease of use for decision makers, particularly in these non-traditional areas. For the covering abstract see ITRD E135582.
Abstract