The wrong side of the tracks: quantifying barrier effects of transport infrastructure
Paper in proceedings, 2018
Cities can be characterized as distributions of accessibility. Two elements in the urban fabric that influence this distribution of accessibility are motorways and railways. These are powerful connectors in urban traffic systems, but can also create strong barriers on a local scale. Based on a literature review, the negative effects – also called severance– of these barriers on social inclusion, health, and access to workplaces are described. Furthermore, it is pointed out that barrier effects are determined by three elements: transport infrastructure, built environment and people’s wishes and needs.
Decisions concerning infrastructure projects are usually based on extensive effect assessments of the project. These assessments are based on the quantitative measurement of a wide range of effects, but the assessment of barrier effects is commonly based on subjective, qualitative methods. As a consequence of this, the detrimental effects that barriers can have on city life run the risk to be undervalued or not taken into account at all.
This paper presents two new morphological indicators with which some of the barrier effects identified in the literature review can be quantified. One indicator is related to proximity to facilities, measured by network distance. The other relates to accessible offer of facilities, measured as the number of facilities within a given metric radius from each residential address.
The indicators are tested in a case study in Gothenburg, Sweden, where a four-lane motorway and a railway track form substantial restrictions on the urban development of a former harbour area in the centre of the city. In the case-study, the consequences of placing the infrastructure in tunnels are assessed. The analyses show how the increases in proximity to facilities and in accessible offer of facilities are distributed in non-linear patterns. These results demonstrate the importance of taking into account transport infrastructure, built environment and people’s wishes and needs when assessing barrier effects.
The case study indicates the potential of the proposed indicators for inclusion in a method for the quantification of barrier effects. With such a method, the reduction of barrier effects can potentially be prioritized in decisions concerning transport infrastructure, which can have far-reaching societal impacts; from an increase of accessibility to facilities and people to improving health by creating more potential for active travel. Furthermore, a method for quantification could provide local stakeholders such as municipalities and local communities with objective arguments in negotiations about infrastructure projects.