Robustness of Accessibility Challenges to Land Use Developments
Barry Zondag, Significance, Eric Molenwijk, Rijkswaterstaat - WVL
The study of the robustness of accessibility challenges to land use developments for regions in the Netherlands shows which regions are most sensitive and where land use measures are promising to improve accessibility.
The Ministry of Infrastructure and Environment of the Netherlands executes, in general with intervals of four years, a national transport market and capacity analyses to inform the newly elected government about the future accessibility challenges. The insights from this analysis are used to select and prioritize in which regions a further exploration of the accessibility challenges will be started potentially resulting in an investment program. The future accessibility challenges are explored under two long term demographic and socio-economic scenarios to address uncertainties in economic and demographic developments. Additionally in this study the robustness of the future accessibility challenges is explored for alternative land use developments for urban regions within the Netherlands.
The study aims to deliver insights on: a) robustness of accessibility challenges to land use developments by region b) contribution of spatial strategies to improve regional accessibility. The study addresses these research challenges at two different levels of spatial detail. At the national level land use developments for all urban regions in the Netherlands are tested on their impact on accessibility. At a regional level this is done for the larger Amsterdam region. The national analysis is used to differentiate between regions where the accessibility challenges are more or less sensitive for alternative land use developments.
The impacts of the various land use alternatives are calculated by applying the TIGRIS XL model, a land use and transport interaction model for the Netherlands. The accessibility challenges are discussed by a broad set of accessibility indicators covering accessibility of jobs by car, public transport and bicycle, network aspects, such as congestion, and accessibility benefits in monetary terms. In the regional analysis for the Amsterdam region this set is extended with a bottleneck indicator for the road network enabling to address the impacts of land use developments on specific bottlenecks.
The calculation results show that a more or less concentrated urban development has a substantial impact on the accessibility of jobs. The type of urban development has especially a high impact on the accessibility of jobs by bicycle which is an important mode of transport in urban areas in the Netherlands. If around 20% of the future housing plans (which covers around 3% of total houses) is located at a different location (more urban or suburban) then the accessibility of jobs by bicycle changes between +4% and -7,5%. The impacts of urban patterns on accessibility by public transport are also substantial, between 2% and -5%, and the accessibility of jobs by cars is least sensitive between 1.3% and -3.3%.
The land use variants also have an impact on national and regional congestion levels and an increased urban densification slightly reduces congestion levels and vice versa suburbanization increases congestion levels. At a more detailed level of network elements, land use variants typically results in both locations with increased and decreased congestion levels. The analysis applied for the Amsterdam case demonstrates a substantial impact of land use developments on size and location of bottlenecks in the region. This indicates for this region a low robustness of the accessibility challenges to uncertain future land use developments.
An estimation of the accessibility benefits for all modes and travel purposes (excluding freight) shows that the benefits of land use variants are comparable in order of magnitude with a long term and large scale road infrastructure investment program. The composition of the accessibility benefits is different between the two type of measures and proximity benefits are the dominant benefits of land use measures instead of speed/travel time benefits. Another element is that land use measures have substantial accessibility benefits for travelers by public transport and especially active modes like bicycle and walking. This also means that different population segments, differentiated by car access or income classes, benefit of land use changes.
The insights on regional differences in the sensitivity of congestion and accessibility of jobs (by car, public transport and bicycle) to land use developments are combined into a regional robustness indicator describing the sensitivity of accessibility challenges in a region. The robustness indicator differentiates between more and less robust regions. In less robust regions land use developments should play a more active role in the evaluation of infrastructure investments to check the robustness of the outcomes. Further land use strategies should be considered more profoundly as an policy instrument to address accessibility challenges in these regions.
Association for European Transport