Urban densities foster shorter network lengths

One argument for containing urban densities is that cities need a critical population density to sustain sufficiently available public transportation. However, the question of whether denser cities foster shorter public transport networks empirically is problematic, because real-world transport nets are a product of many additional factors that are presumably not related to urban form. I have recently published a paper in which I adopted a network expansion simulation approach to generate and analyze counterfactual data on network lengths for 36 world cities. To do so all networks are generated with similar expansion restrictions and objectives. Denser cities are found to have shorter simulated public transport networks, regardless of the tested model parameters. This provides additional proof that densities are needed to facilitate the provision of proximate public transport infrastructure, with potentially self-reinforcing effects.

The paper is published here. The GeoDMS scripts to generate counterfactual networks can be found on my github.

Transport Link Scanner

It has repeatedly been noted that there is a clear logic behind the geographical expansion of transport networks. That implies that one can model how those transport networks expand geographically; and how the final network would change if the network is constructed with different objectives.

In the last years I have developed the so-called Transport Link Scanner model, which is a GeoDMS based tool that allows the exploration of the effects of economic context and policy preferences on transport network expansion. The model combines a conditional logit model, some heuristics and techniques from the literature on corridor location problems and transport modelling methods to simulate the most likely network after the introduction of a new transport innovation.

The most recent version of Transport Link Scanner can be downloaded through this page. The scripts are downloadable here. The data is available here. Instructions to get you started are available here.

The effect of railroad network expansion on travel times in the Netherlands

The construction of overland transport infrastructure has had a major social and economic impacts by reducing travel costs and travel times. One of the key questions I am interested in is how travel time improvements have changed the level of accessibility and interaction opportunity within territories. I have made this movie to demonstrate the extent in which historical railroad construction in the Netherlands has affected travel times to the country’s capital, Amsterdam. Greater travel time improvements are demonstrated by lighter hues. The actual year is shown in the upper left corner.

To me, the movie and underlying data show two important things: first, that railroad construction has substantially altered travel times; second, that the largest improvements in travel times were realized in the first stages of railroad network development. The latest stages, when numerous local lines were added to the network, have much less effect on travel time savings.