Over the last 15 years the model has been continously improved and the version currently in use is TIGRIS XL version 7. Significance has carried out these developments commissioned by the Ministry of I&W and PBL. The model was recently positively assessed by an external visitation committee consisting of six academic experts.
TIGRIS XL has a modular structure and, in addition to the transport model (national model system LMS), consists of four modules, for demography, land and real estate market, housing market and labor market respectively. Figure 1 provides an overview of the architecture of the system with these modules, their main interconnections and the interactions with the transport model. The demography module models the composition of the population per zone, both the number of people per sex and age group and the number of households by type (economic activity, income, children).
Figure 1: Functional design of the TIGRIS XL model (source: Zondag et al. 2019)
The housing market module focuses on housing demand, housing prices and match between supply and demand in the housing market. The housing market module contains estimated nested logit models for the housing preferences, by location and type of house, of 14 household types estimated on housing market survey data for the period 2006-2015. This module has a close interaction with the land market and real estate market module that simulates changes in land use types and the development of new houses. Finally, the labor market module models the location of jobs and the labor participation of the labor force. The location preference for workplaces has been estimated for seven different economic sectors based on historical time series data on employment at the level of transport zones. The spatial distribution of jobs and population by segments is input for the transport model.
The TIGRIS XL model covers a broad policy area, from developing scenarios to calculating the structuring impacts of infrastructure measures, and the model has been used for various policy purposes and studies, such as:
– Add spatial component to multi-sectoral national scenarios, Tigris XL monitors the consistency in space (between regions) and sectors (including population and jobs), examples are the spatial explorations study, the Welfare and Living Environment study, the study of the Delta scenarios for the water sector and the future of the Netherlands study (weighing up land demand and supply);
– Calculating the impacts, on accessibility and sustainability of urbanization options or integrated spatial and transport perspectives. The added value of Tigris XL, compared to standard transport models, is that the spatial consequences of the urbanization options and infrastructure policies are calculated endogenously. Examples of studies are the national studies on accessibility effects of urbanization (Zondag, 2016), spatial robustness of accessibility (for I&W) and regional studies for the MRDH region, the A2 corridor and the MRA region.
There was an academic visitation in 2019/2020 and the main conclusions of the audit report are: the model is state-of-the-art / state-of-the practice, suitable for its current use and further development is necessary to to be fit-for-use in the future (https://www.pbl.nl/publicaties/naar-een-nieuw-tigris-xl).