Performance Measures of Road Infrastructure - A Life Cycle Thinking Approach

Doktorsavhandling, 2019

Roads have been an important asset of human society and the approach we adopt towards planning, designing, constructing, operating, and maintaining of the road infrastructure has significant consequences in the long-term for not only the humans, but all species on planet Earth. Hence, the lifecycle performance of the road infrastructure that sustain our socioeconomic development with a low environmental impact, while fulfilling their technical and functional requirements is of critical importance and needs to be improved. This thesis aims to understand the nature of the information that helps improve the performance of road infrastructure over their lifecycle and propose solutions that close the existing research gaps.

This thesis is essentially divided into two parts. In the first part, it focuses on the current lifecycle thinking towards the public physical infrastructure. It carries out a survey of the literature to gain a holistic understanding of the current challenges that infrastructure faces, namely population growth, anthropogenic greenhouse gas emissions, land use and coverage change, and abiotic depletion. It then recommends potential approaches to close the identified gaps. The investigation reveals that considering the entire lifecycle of the infrastructure helps avoid partial thinking, which affects the mankind and the ecosystem adversely and results in problem shifting. It shows how the lifecycle-based methods that incorporate uncertainties help enhance the depth of understanding and decisions regarding the lifecycle performance of infrastructure. In addition, it advocates that the collaboration between and within different fields of science and practice needs to be increased to better capture the consequences of various risks and avoid adverse effects.

In the second part, a systematic desk (or secondary) research and regular interactions with the Norwegian Public Road Administration (NPRA) were carried out which revealed the following research gaps to improve the environmental and economic performance of the Norwegian road networks: (1) measure environmental performance of the construction machinery over their entire lifecycle based on regionalized data, which helps increase both the resolution and exclusiveness of the results; (2) estimate lifetimes of pavements based on their technical performance, which helps in improving the validity of the results when benchmarking different pavements with respect to different criteria, e.g., environment, economy, and society, and supports the decision-making at different phases of road infrastructure projects; and (3) capture material flows and stocks of road infrastructure, which helps get an overview of the availability in terms of quantities and time of the secondary materials to theoretically substitute the virgin/primary materials. Hence, potential approaches were used by means of different methods and models, namely geographical information systems (GIS), life cycle assessment (LCA), survival analysis, decision tree model, and material flow accounting (MFA), for the three focus areas to bridge the identified gaps. Also, the Norwegian input data were applied to show the proposed approaches quantitatively. Findings from the research carried out in the second part of the thesis show that:

·       Although the operation phase of the construction machinery has been studied solely in most of the prior research, the investigation in this research showed that the inclusion of the other phases is equally important. This means that the production, delivery, maintenance, dismantling, waste processing, and circulation of energetic and non-energetic materials at different phases of a machine’s lifespan contribute to the overall environmental impacts.

·       The proposed approach to measure the durability of the pavements showed discrepancies between the maintenance records and the technical requirements and explained how different factors increased or decreased the lifetimes of pavements in different traffic classes. In addition, the results from the statistical tables (showing relative values) were transformed to absolute values to ease the readability and comparability of lifetimes between different pavements.

·       The amount of stock in the Norwegian road network has continuously increased and in 2017 there were about 420 Mt of road materials in-service. The growth was owing to the continuous expansion of the road networks. However, the growth in the amount of road stock was predicted to increase by 9 % – 10 % between 2018 and 2050 as well, though it was assumed that the network would not expand after 2017.