Developing a sustainability rating framework and indicator decision sub-logic for highway design and construction sector in Nigeria

Highway infrastructure development projects improve living standards across communities and cities, and increase the economic growth and societal expectations of a country. Due to anthropogenic activities, the use of sustainability strategies is encouraged for highway infrastructure development. However, knowledge of and practical approaches towards sustainability implementation in highway development is lacking in the literature for Nigeria. A literature review has identified and categorised sustainability gaps in Nigeria's highway development. These are categorised into four groups for design (technical, environmental, economic and social) and six groups for construction (social, environmental, economic, engineering, project management, and health and safety). A mixed-methods approach is used for data collection. A questionnaire survey was issued to 33 design and 100 construction project-level participants to assign values to the indicators using the psychometric Likert scale. Afterwards, the analytical hierarchy process (AHP) was utilised to determine pairwise comparison data collection to measure the weighting values of each indicator. Fifteen experts participated in qualitative interviews and data were thematically analysed. Face-to-face interviews were conducted with fourteen project-level experts in ongoing highway projects in Nigeria as a project case study, to measure the effectiveness of the indicators developed in this research. Correlation variance of the indicator results between the Likert scale and AHP aided in selecting 36 design and 53 construction indicators, using low, middle and high priority ranking. This research identified project-level participants' expectations on the sustainability agenda, such as sustainability being considered a world-view requirement for project development and human survival. From the project case study, sustainability gaps were identified. This research developed an integrated highway sustainability framework with indicator decision sub-logics. This research argues that implementing an integrated framework and indicator decision sub-logics promotes sustainability awareness and reduces unsustainable highway development practices across Nigeria. This thesis has provided insight adding to the existing body of knowledge on innovative sustainability practices for Nigeria. It has also established an integrated sustainability framework to reduce the adverse impact of unsustainable construction practices across Nigeria's highway development.