Beyond expected travel time: Unveiling the role of ergodicity breaking in mobility decisions and effective transportation policy

In this paper, we direct the attention of the mobility science community to the concept of ergodicity-breaking, a principle of importance for understanding and addressing the complexities of (personal) mobility. Ergodicity refers to the assumption that a system’s evolution over time can be approximated by its ensemble average at one time step: an assumption whose validity has been increasingly put into question. Through a series of thought experiments, we illustrate the non-ergodic properties of travel time. These experiments reveal a new perspective of an old adagio, “People value reliability” more so than transportation speed. We show that this statement does not necessarily stem from heuristics, biases, or idiosyncrasies but rather that it is a consequence of the environment and dynamic in which people make modal choices. Our approach could be a powerful tool for instilling behavioural change. We offer new insights into inducing modal shifts and improving urban mobility systems. Thanks to this shift in perspective, the analytical frameworks used in mobility science could also include non-ergodic dynamics, thereby enriching our understanding and approach to creating more effective mobility interventions and policies. • Transport choices occur in a non-ergodic world. • Our model and thought experiments show reliability beats speed in travel. • With absorbing boundaries, reliability, not personal preferences, drives choices. • Reliability is the critical determinant for modal shifts.