Abstract (EN):
The Netherlands National Model System (NMS) is known as one of the first disaggregate national travel demand forecasting systems used in practice. The model system has been in use since 1986, and has been extensively updated and extended through its lifetime (for a brief description of the model and an overview of similar demand systems see Fox et al, 2003 or Daly and Sillaparcharn, 2008). Since its origin the model has been applied in numerous policy analysis for national road and railway planning alternatives, such as infrastructure investments, and pricing- or management policies.
The Dutch Ministry of Public Works and Water management recently issued an update and extension of the National Model System and its regional counter parts (see Smit et al., 2009). The choice models in the current version were estimated almost 10 years ago on survey data from 1995 (Hague Consulting Group, 2000b). A first objective is to update the modelling system by re-estimation of the choice models in the system on the National Travel Surveys for 2002 and 2003. In addition to that the re-estimations allowed a revision and further improvement of the model system.
One of the innovations in the update of the LMS, is the estimation and implementation of an integrated nested choice structure. This improves the coherence of the different choices in the modelling system through the inclusion of logsums from subsequent choices in the estimation of the modules.
One of the issues addressed in this paper is to improve the inclusion of accessibility effects on tour frequency (TF). In spite of its intuitive importance and the consequent political need to account for such an effect to address latent demand when the infrastructure is improved, the current version of the NMS lacks an inclusion of accessibility attributes in the TF module (Hague Consulting Group, 2000b). This is remarkable since most transport demand models that are based on disaggregate choice models do include accessibility effect (Fox et al.; 2003). In an overview of a selection of studies Daly (1997) shows that significant accessibility parameters can be obtained in TF models, as long as an appropriate measure and demand segmentation has been applied. The most appropriate measure is the logsum from mode/destination (MD) choice model for the respective travel purpose. In the current update of the NMS this issue is addressed by estimating parameters for purpose specific logsums from the MD models in the trip frequency estimations.
A further advancement is made by integrating the MD and car time-of-day (ToD) models into a single model. This model is estimated by a simultaneous SP/RP estimation; the RP travel survey data of MD choices are enriched with SP data on time-of-day and mode choice. This makes different nesting structures possible: time-of-day choice can be higher, lower or on the same level as destination choice. Additionally, the socio-economic segmentation of the MD model is improved, and the non-motorised modes are split into walking and cycling. The paper discusses these enhancements and their consequences.
For train travel a new model of station choice and access/egress mode choice has been developed. This is a major improvement for the implementation of train scenarios. The logsum from this model is used in the MD choice utility function to improve and the way train level-of-service affects MD and TF choices and to make the model system as a whole more consistent. The system is now thus specified as a single decision tree that comprises train access/egress mode choice, station choice, time of day choice, destination choice, main mode choice and tour frequency choice.
Language:
Portuguese
Type (Professor's evaluation):
Scientific