Towards sustainable pavements : a reference document

Abstract

A sustainable pavement has to be economically, socially and environmentally feasible at an acceptable level of risk over its design life. Practically, a sustainable pavement optimises a range of performance indicators including cost, functionality, safety, local economic and human development, emissions, climate change and resource use, amongst others, which is measured by using a suite of assessment methodologies.

This thesis focusses on providing practical guidelines to characterise and evaluate the sustainability of a pavement. The objectives focus on a practical systems framework, populated with various methodologies and data sets, for the analysis of holistic pavement sustainability in South Africa. The overall scope of this thesis is the field of pavement sustainability focussing on environmental and social tenets. Sustainability contributes to the state of knowledge by defining pavement sustainability, developing a life cycle inventory, creating a social life cycle inventory, determining climate change assessment, doing a cumulative risk assessment, determining a sustainability index and providing an improved understanding of issues relevant to pavement sustainability.

These methodologies include life cycle cost analyses, life cycle assessments, social life cycle assessments, performance evaluations and climate change assessments amongst others. Apart from a life cycle cost analysis few methodologies have sufficient-evidence-bases from which to draw confident results. The methodologies are rarely aligned to evaluate holistic sustainability. The fast pace of methodology development has also arguably left behind gaps in research. Most notably is the consideration of risks that may affect sustainability.

Firstly, sustainability is an interrelated concept since the modification of one sustainable indicator affects the others. Secondly, changes to or addition of indicators, if not properly evaluated, may cause unanticipated and significant reduction in sustainability outcomes. It is essential to develop required evidence bases for these methodologies to enable holistic evaluations and provide for optimal pavement infrastructure provision in South Africa.

Although this thesis provides an improved comprehension of holistic pavement sustainability, much still needs to be done to improve this understanding and merge the various concepts into a clear and concise framework. The recommendations in this thesis should be elaborated to ultimately aid in the sustainable development and management of South African pavement infrastructure.