Steady-state link travel time methods: Formulation, derivation, classification, and unification

•Unifying steady-state link travel formulations for three perspectives (functional longitudinal, functional cross-sectional, and experienced) and across three modelling paradigms (dynamic, semi-dynamic, static).•All formulations are derived from a state-of-the-art continuous time macroscopic first order network loading model of the Generalised Link Transmission Model (GLTM) family.•Demonstrating functional and experienced perspective formulations yield identical results regardless of their difference in context.•Explicit derivation for a number of existing formulations in the literature, which are to be considered special cases of our more general formulation.•Classification for a large number of existing formulations is provided as well as numerical examples to highlight the use of various perspectives.