Divisive connections: Theory and tools for the quantification of barrier effects in transport infrastructure projects

Doctoral thesis, 2022

Transport infrastructure increases regional accessibility but at the same time it creates barriers that reduce local accessibility. These barriers reduce social contacts between people, and limit access to services and leisure. Barriers make cycling and walking less attractive, which has negative impacts on health, and can lead to increased emissions from cars. Assessments of barrier effects are commonly based on general descriptions and rough estimations, although methods for the quantification of these effects have been developed. Reasons for not using these methods are: limited dissemination, difficulty in separating barrier effects from other effects, and differences in the terminology that is used to describe them.

This thesis aims to make existing academic knowledge and tools regarding the quantification of barrier effects more applicable in practice. The thesis presents a conceptual model that defines five determinants of barrier effects: Transport features, Crossing facilities and street network, People’s abilities, Land use, and People’s needs, and defines three levels of barrier effects. Further, the thesis lists indicators and methods for quantifying barrier effects. The model and indicators are studied in two case studies. In the first, four of the indicators were operationalised in a transport infrastructure project using conventional GIS tools. In the second, the indicators were studied in an ongoing transport infrastructure project using an action research approach. In this study, participants reported how the barrier effects analyses contributed to the impact assessments with transparent and precise support, which allowed the stakeholders to solve a long-standing conflict about the localisation of the infrastructure. One of the central issues that was revealed is the need for collaboration in order to create input material for the analyses.

Based on these results, the main finding of this thesis is that knowledge of both social and technical processes in the assessment of barrier effects is required for making existing academic knowledge and instruments more applicable in practice.