Abstract :
[en] Urban public transport systems have attracted increasing academic attention over the past two decades, driven by rapid urbanisation, demographic growth, and the need to sustainably improve user mobility conditions. Existing research has focused on key research areas, including user satisfaction, accessibility, governance, and the formalisation of public transport, with the overarching aim of improving urban mobility. However, these approaches remain largely fragmented, resulting in a persistent binary categorisation that distinguishes between so-called ‘formal’ and ‘informal’ transport. This dichotomy, widely used in the literature, is typically based on subjective or context-dependent criteria and is rarely grounded in explicit and comparable standards. As a result, informal transport is frequently associated with cities in developing countries, whereas formal transport is generally linked to urban contexts in developed countries. At the same time, a growing body of research has highlighted the functional, economic, and social advantages of services classified as informal, advocating their integration into contemporary urban planning strategies. The coexistence of these perspectives has led to a proliferation of heterogeneous and sometimes ambiguous terminologies, such as paratransit, semi-informal transport, and non-conventional transport, reflecting the absence of a unified conceptual framework. In response to this fragmentation, this thesis develops a critical and integrative review of the existing literature, conceptualising formalisation as an overarching analytical framework for organising diverse strands of research. Building on this foundation, it introduces a quantitative model, the Public Transport Formalisation Level (PTFL), based on a point-based system designed to measure the degree of formalisation of public transport systems using a structured set of indicators derived from both scientific and grey literature. The findings demonstrate that the formal/informal dichotomy represents an oversimplification of empirical reality. Instead, public transport systems are better understood as operating along a continuum of formalisation, within which services with varying degrees of formalisation coexist across all urban contexts. Empirical analyses, based on case studies conducted in several African cities as well as in the Liège–Verviers region in Belgium, confirm the validity of this approach and highlight the universal and transferable nature of the formalisation continuum. The results indicate that transport systems in the African cities studied are not entirely informal, but rather exhibit moderate levels of formalisation, with PTFL indices ranging between 40% and 60% (Class C), with some cities reaching Class B (i.e. PTFL levels above 60%). By contrast, the TEC system in Liège–Verviers appears well formalised, with formalisation levels between 60% and 80% (Class B). These findings reveal relatively limited gaps in formalisation between the contexts examined, thereby challenging the traditional dichotomy between formal and informal transport and confirming the coexistence of formal and informal transport options across all urban settings. By reducing terminological complexity and introducing a unified and operational framework, this thesis contributes to advancing the comparative analysis of urban public transport systems at the international level.
