A prevailing concern in higher education, especially within the fields of Science, Technology, Engineering, and Mathematics (STEM), often refers to underrepresentation of certain social groups. While the public attention is drawn to the aggregated statistics reflecting participation issues at a macro societal level, the essence of the debate is the real underrepresented individuals behind each number that have been hindered by any tangible or impalpable reasons. Thus, how to address existing disparities in education systems by looking beyond the aggregate number to the nuanced barriers faced by different groups becomes vital. Based on a systematic literature review, this research aims to explore the complex barriers and opportunities regarding the expansion of participation in STEM education. By analyzing global examples, the study identifies socioeconomic disadvantages, exclusionary institutional practices, and internal psychological barriers such as low confidence, lack of belonging, and stereotype threat as key factors that hinder the engagement of marginalized communities in STEM fields. Drawn on a meta-analysis, the research also evaluates successful intervention practices, such as role model-based initiatives and inclusive educational environments, and values-affirmation exercises, which have been shown to improve motivation, strengthen self-efficacy, and increase retention in STEM. Additionally, the study synthesizes these findings to propose systemic reforms at individual, institutional, and governmental levels. In summary, this research offers evidence-based and actionable strategies, leading to a more inclusive STEM landscape for sustainable development.

Given the significant role of asphaltic pavement in surface transportation systems, even minor enhancements in asphalt materials hold the potential for cost savings and reduced environmental impacts. The healing properties of asphalt have drawn interest for sustainability, yet much remains unknown about the causes and influencing factors. To leverage self-healing for extending pavement life, understanding the mechanisms and conditions that stimulate microcrack healing is essential. This study aims to investigate the dynamic progress of microcrack closure in asphalt mastics. The time-series evolution of crack closure led by self-healing is tracked by neutron computed tomography, with image processing facilitating volumetric analysis over a 7 h period. The study examines the healing process in mastic samples with three different sand filler contents (10, 20, and 30%). Results show that for all the investigated samples, the healing rate declines exponentially over time, with 100% recovery not achieved after 7 h at room temperature. Filler content-influenced healing speed and 20% sand demonstrate the best performance. Meanwhile, the healing performance varies within the 10% and 30% groups, depending on initial crack size. Additionally, the study finds that initial crack size influences healing behavior in the samples.

Grounded in the context of global climate change and the pressing demand for carbon-neutral practices in road infrastructure management, the road sector has had a long history of extensive efforts to pursue sustainability. However, navigating the complex road and pavement system to the circular economy is a multi-dimensional and time-consuming endeavour. Obstructed by lock-in mechanisms of the prevailing "take-make-dispose" linear mode, the current circular economy studies in road engineering often focus only on one certain type of practice, featured by fragmentation from a system perspective. To assist the systemic circular transition of the road sector, this doctoral thesis offers a comprehensive retrospection on the current road management system and aims to find pathways to kick off this transition with the opportunities brought by digitalization and electrification in the Industry 4.0 era.

In order to understand the current status of road infrastructure management and the hurdles to the transition, this thesis began with a historical lens and established two systematic literature reviews that have summarized the traditional practices in road and pavement management, which have also provided a structured investigation of the research gaps and barriers towards the future transformation of smart road infrastructure. The conclusions from these two reviews indicate that marginal changes in the current practice of road management will only lead to burden shifting, instead of enabling the occurrence of the circular transition. One of the key conclusions is that the onset of the transformation process needs systemic thinking and collaboration among stakeholders.

Therefore, based on two case studies in Sweden, this thesis takes a step further to find the alignment between technical complexity and actor complexity and find the pathways to the transition with systemic-level solutions. By applying multidisciplinary knowledge from management science, these two case studies exemplify how to create a common vision for sustainability with active stakeholder participation, offering an important aspect of the effective navigation towards the sustainability transition in the road sector. With different research focuses and diverse combinations of tool-kits in these two case studies, the first case study on Digital Transport Southern Stockholm emphasized the importance of bridging the gap between authorities and the industry and involving all relevant stakeholders in a more dynamic way; and the second case study on Zero-emission Contracting SödertörnCrosslink suggested a sector-wide readiness to embrace change, contingent on shifting responsibility to the market.

In synthesis, the thesis calls for a holistic approach that balances technical, environmental, and social dimensions of sustainability, guided by clear definitions, flexible frameworks, and stakeholder engagement. It puts emphasis on mutual efforts towards realizing a sustainable, circular road sector adaptable to evolving global sustainability agendas. Through its enriched narrative, the thesis contributes to broader discussions on sustainability transitions, offering insights applicable across infrastructure development domains.

Förankrad i sammanhanget av global klimatförändring och det påträngande behovet av koldioxidneutrala metoder inom förvaltningen av väginfrastruktur har vägsektorn haft en lång historia av omfattande ansträngningar för att främja hållbarhet. Att navigera det komplexa väg- och beläggningssystemet mot den cirkulära ekonomin är emellertid en mångdimensionell och tidskrävande strävan. Hindrad av låsningar i det rådande linjära take-make-dispose-läget fokuserar de nuvarande studierna inom cirkulär ekonomi inom vägteknik ofta bara på en viss typ av praxis, vilket leder till fragmentering ur ett systemperspektiv. För att underlätta den systemiska cirkulära övergången inom vägsektorn erbjuder denna doktorsavhandling en omfattande återblick på det nuvarande vägförvaltningssystemet och syftar till att hitta vägar att påbörja denna övergång med de möjligheter som digitaliseringen och elektrifieringen för med sig i industrin 4.0-eran.

För att förstå den aktuella statusen för förvaltningen av väginfrastruktur och hindren för övergången började denna avhandling med ett historiskt perspektiv och etablerade två systematiska litteraturgenomgångar som har sammanfattat de traditionella praxiserna inom väg- och beläggningsförvaltning, vilket också har gett en strukturerad undersökning av forskningsgap och hinder mot den framtida transformationen av smart väginfrastruktur. Slutsatserna från dessa två översikter indikerar att marginella förändringar i den nuvarande praxisen för vägförvaltning bara kommer att leda till överföring av bördor, istället för att möjliggöra förekomsten av den cirkulära övergången. En av de viktigaste slutsatserna är att starten av transformationsprocessen kräver systemiskt tänkande och samarbete mellan intressenter.

Därför, baserat på två fallstudier i Sverige, tar detta avhandlingsprojekt ett steg längre för att hitta samklangen mellan teknisk komplexitet och aktörskomplexitet och hitta vägarna till övergången med lösningar på systemnivå. Genom att tillämpa tvärvetenskaplig kunskap från förvaltningsvetenskap exemplifierar dessa två fallstudier hur man skapar en gemensam vision för hållbarhet med aktiv deltagande från intressenter, vilket erbjuder en viktig aspekt av den effektiva navigeringen mot hållbarhetsövergången inom vägsektorn. I dessa två fallstudier används olika forskningsfokus och verktygsuppsättningar. Den första fallstudien, Digital Transport Southern Stockholm, understryker vikten av att minska klyftan mellan myndigheter och industrin genom att dynamiskt engagera alla relevanta intressenter. Den andra fallstudien, Nollutsläppsentreprenad Tvärförbindelse Södertörn, framhäver behovet av en sektorsövergripande beredskap för att anamma förändring, vilket innefattar att överlåta mer ansvar till marknaden.

I syntes efterlysar avhandlingen för en holistisk ansats som balanserar tekniska, miljömässiga och sociala dimensioner av hållbarhet, vägledd av tydliga definitioner, flexibla ramverk och deltagande från intressenter. Den uppmanar till gemensamma ansträngningar för att förverkliga en hållbar, cirkulär vägsektor som är anpassningsbar till utvecklingen av globala hållbarhetsagendor. Genom sin berikade berättelse bidrar avhandlingen till bredare diskussioner om hållbarhetsövergångar och erbjuder insikter som är tillämpliga inom infrastrukturutvecklingsområden.

Navigating the complex pavement system to the circular economy is a multi-dimensional and time-consuming endeavour. Obstructed by lock-in mechanisms of the prevailing “take-make-dispose” linear mode, the current circular economy studies in pavement infrastructure often focus only on one certain type of practice, featured by fragmentation from a system perspective. This study presents the first systematic literature review on the historical development trend of the circular economy concept in the pavement sector based on the collected 59 studies from 2006 to 2022. This review also identifies the soft (regulatory, social/environmental) and hard (technical, market/economic) drivers of- and barriers to the paradigm shift, aiming to coordinate the existing fragmented findings and facilitate the future systemic implementation of the circular economy. The synthesis of the results indicates that the underdeveloped technical guidance and legal system are inhibiting the paradigm shift to the circular economy. Furthermore, the authors argue that the importance of transparent and standardized data along the whole supply chain should be highlighted. Ultimately, this paper suggests that a welcoming environment set by the road authorities is crucial for innovation and entrepreneurship, as well as for constructing a system where stakeholders can confidently take responsibility and initiative.

Based on the publications from two databases during 1998–2020, this paper presents a systematic literature review on pavement maintenance effectiveness evaluation to summarize the current trend and identify the research gap that must be addressed for a sustainable maintenance management. This review has analyzed and synthesized maintenance thresholds and their mechanisms, the measurement methods of effectiveness in terms of performance, cost and environmental impacts. In particular, this paper has critically examined the state-of-art maintenance effectiveness optimization strategy that has included environmental concerns and sustainable goals, in comparison with the traditional cost-effectiveness evaluation method. The study has revealed the ambiguous definition of pavement maintenance effectiveness and data availability have caused inconsistencies in the evaluation process; moreover, the embryonic pavement life cycle assessment studies and limited study on pavement use phase have set obstacles in the expanding system boundary of sustainable maintenance effectiveness evaluation.

Pavement system plays an indispensable role in the socio-economic and sustainable development of every modern society. Yet, pavement construction and maintenance is also responsible for a significant fraction of the GHG emissions from the whole transport sector. At the same time, the extensive global pavement network entails continual investment in maintenance and rehabilitation activities. Given the evidence from previous studies, pavement maintenance has a great potential in reducing pavement-induced GHG emissions and fuel consumption. To assist the transition towards a future sustainable road infrastructure, this thesis has marked the theoretical basis of sustainable pavement maintenance management. Two approaches are discussed to offer a multi-dimensional view for future sustainability improvement in pavement maintenance practices. With the still-evolving concept of sustainability in road infrastructure, it is necessary to recognize where we are and what we need to do to develop a comprehensive management framework with the opportunities and challenges. Based on a systematic literature review, this project identifies the current stage of sustainable road infrastructure management and guides to sustainability-oriented maintenance optimization for designing top-down strategies. Meanwhile, it is not enough to only optimize the decision-making process; more bottom-up knowledge of pavement materials is required to inform better maintenance design. This thesis has focused on the self-healing property of asphalt material due to the non-negligible sustainability indications it implies. By applying neutron tomography and image processing technique, the microstructural changes during the self-healing process are analyzed with its 7-hour time-series volumetric data. The experiment has shown that different filler content has a great influence on self-healing efficiency in asphalt mastics. The results will give us the possibility to optimize asphalt self-repair, shedding a light on a new generation of sustainable asphalt pavement. The two approaches presented in this thesis offer valuable insights into sustainable road infrastructure optimization from different aspects.

I varje modernt samhälle spelar vägarna en viktig roll för socioekonomisk och hållbar utveckling. Vägnätet, med byggande och underhåll, bidrar också med en betydande del av växthusgasutsläppen från hela transportsektorn. Vägnätet kräver kontinuerliga investeringar på grund av behovet av underhåll . Tidigare studier har visat att det finns en stor potential för minskning av utsläppen av växthusgaser från vägunderhåll. Vägarnas kvalitet spelar också roll för trafikens bränsleförbrukning. 

Fokus för denna avhandling är att underlätta för framtida hållbar väginfrastruktur. När det gäller den teoretiska grunden för hållbar förvaltning av vägar och underhåll av vägbeläggningar är det nödvändigt att förstå vad som är dagens aktuella teknik, och också att veta vad vi behöver utveckla för att få ett heltäckande ledningsramverk för vägunderhåll. Här finns både möjligheter och utmaningar. Baserat på en systematisk litteraturgenomgång identifierar detta projekt det aktuella läget när det gäller praktik för förvaltning av väginfrastruktur. Som ett resultat av detta presenteras olika metoder som tillämpas för en målorienterad underhållsoptimering, som måste göras top-down från den som har övergripande ansvar för vägnätet. Samtidigt räcker det inte att bara optimera beslutsprocessen, det krävs mer bottom-up kunskap i fråga om beläggningsmaterial för att förbättra metoderna för underhåll. Denna avhandling har därför också fokuserat på den självläkande egenskapen hos asfaltmaterial. Här fanns en unik möjlighet att tillämpa neutrontomografi och bildbehandlingsteknik för analyser av de mikrostrukturella förändringarna under självläkningsprocessen i asfaltmaterial, med 7-timmars tidsserievolymetriska data. Experimentet har visat att olika innehåll av fyllmedel i asfaltmastixen  har stor inverkan på självläkandets effektivitet. De två tillvägagångssätten som presenteras i denna avhandling ger värdefulla insikter om hållbar väginfrastrukturoptimering ur olika aspekter. 

The Industry 4.0 era brings new potential to a climate-neutral society with several good technical solutions through digitalization, automation, and electrification. Within the road construction sector, the absence of a "first mover" mechanism, complex stakeholder networks, misaligned incentive structures, shared versus individually owned resources, and a risk-averse mentality all add layers of complexity to adopting advanced technical solutions. Thus, how to effectively kick off a systemic change for innovation and sustainability remains a daunting challenge without a unified answer for the road construction sector, even though ambitious climate goals are often set as part of contracts. Focused on the road project Södertörn Crosslink in Sweden, this study was grounded in a tangible context, enhancing stakeholder involvement and engagement to enable a transition to zero-emission contracting within the road construction sector. It offered a framework based on a combined methodology to lead a participatory approach to identifying challenges, obstacles, and opportunities and together work out a well-founded basis for zero-emission contracting. The findings from this study have resulted in a clear compilation of perspectives that provides insight into possible obstacles to implementation. Through a preliminary system verification and validation assessment, this study has also proposed focus changes and practical models that can continue to be used in the industry to address these hurdles.

Given its fragmented nature and tendency towards natural monopolies, how to systematically kick off or manage the sustainability transition in the transport sector remains unknown. The Digital Transport Southern Stockholm project established an ideal testbed for sustainable transportation transition within a defined area. As part of the project, this study presented real-life examples of the potential opportunities and challenges in an innovation-driven and sustainability-oriented transportation project. Inspired by the success of participatory approaches in assisting system thinking in the field of business management, this research work combined backcasting and game simulation methods to collect and connect the stakeholder perspectives, further addressing uncertainties and providing guidance for navigating the actor and stakeholder complexities inherent during the transition. The results disclosed the missing top-down and bottom-up dimensions in the traditional decision-making structure and emphasized the crucial role of communication and collaboration between sectors with consistent policies, incentives, and fiscal support.

As the asphaltic pavement constitutes a significant part of surface transportation system, even just a slight improvement in the asphalt materials can potentially lead to benefits regarding the cost and environmental impacts of road infrastructure. Fortunately, the healing property that asphalt material possesses has shown a prospect of sustainability enhancement, which has attracted an extensive number of worldwide researches. However, the causes and influence factors have still mostly remained as unknown. In order to be able to count on the self-healing property for extending pavement service life, a better understanding of the mechanisms and conditions that stimulate the self-healing of micro-cracks in asphalt is needed. This study aims to investigate the dynamic progress of micro-crack closure in asphalt mastics. Non-destructive neutron computed tomography was applied to follow the time-series evolution of self-healing phenomenon and corresponding image processing techniques were utilised to conduct the volumetric analysis over a 7-hour scanning time. The damage healing process in the mastic samples with three sand filler content (10%, 20% and 30%) were tracked and analysed. From the volumetric analysis, it was concluded that the healing rate decreased exponentially after a certain time period and no 100% recovery rate was achieved after 7-hour exposure to room temperature. The results indicated that different filler percentages had an evident effect on the healing speed. It was found that mastics with 20% sand had the best healing performance, while it differed for the 10% and 30% groups depending on the initial crack size. Additionally, it also appeared that the initial crack size affected the healing behaviors in the samples.