Formalisation levels of public transport systems: case study of Liège

Public transport systems currently lack scientific measures to assess their levels of formalisation. This study aims to measure the formalisation of the public transport system in Liège using indicators derived from GTFS data. To achieve this, the indicators were weighted using a point system based on guidelines issued by public transportation authorities. The results show that although a public transport system may be described as formal, informal elements can persist when considering infrastructure and operating conditions. Additionally, transport lines within the same city do not exhibit uniform levels of formalisation. Thus, labelling a transport system as “formal” without scaling its components is a misjudgement that obscures the components of the transport system that require improvement.