The GM4 model is a large-scale disaggregated multimodal tour-based model rooted in discrete choice theory. The model distinguishes 9 modes of transport, 5 home-based purposes, 2 work-based purposes and 3 child purposes. The model consists of a nested Logit structure with a nesting order of the Mode-Destination and Time of Day module estimated by purpose, often as presented in the figure. The model explicitly modelled station choice for train tours and the use of access and egress modes like walking, cycling, bus, tram & metro or car. The model has been estimated on NTS data for the years 2015-2017 in combination with specific survey data for train passengers on their access and egress mode choices and station choices.
Compared to the previous version of the model GM4, the combined Bus/Tram/Metro mode was split into Tram/Metro and Bus and the e-bike was introduced as a separate mode next to conventional bike. Other improvements in the model specification include the use of cost coefficients by income class, car cost specification and reimbursement policies and the use of education level as explanatory variable at production side (population by education level) and attraction side (education level of jobs). In addition to the ‘standard’ model more explorative functionalities have been developed as part of the national model as well. The explorative functionalities are included to explore the impacts of developments such as autonomous vehicles, car sharing and/or MaaS.
In interaction with the client, and an external academic review committee, the resulting models were assessed on many aspect by a wider evaluation framework including the model fit, check on ‘acceptable’ bandwidths for cost- and time elasticities and VTT (based upon literature) and reference values for key transportation figures like mode shares (tours and km) and trip length distributions by mode, both at National level as well as for the 4 largest cities in the Netherlands.
The final model has been formally adopted on 1st of April 2021 by the Ministry of Transport and Water and this model will serve as the standard transport project and policies evaluation tool for the coming 4 years.