Energy use per hour is key determinant of future transport energy consumption

Abstract Transportation is a growing component of global energy consumption. Improvements in efficiency over time have reduced the energy used per kilometre travelled, but so far this has not reversed the increasing energy consumption per person. Instead, due to a complex interplay of factors—including changes in the built environment, shifts in transport modes, and human behaviour—average travel distances have increased, effectively negating efficiency gains. These adaptive dynamics have made it difficult to predict future energy consumption in travel. Here, we present data on remunerated and personal travel covering over half the global population, which supports a simple predictive heuristic based on energy use per unit of travel time, rather than distance. We find that total travel time among 43 countries converges to 1.3 ± 0.2 h d −1 and is invariant with per capita income across two orders of magnitude. This implies that psychological, social, and economic factors lead people to travel for similar daily durations, regardless of wealth, culture, geography, or transport technology, and that built environments and lifestyles co-evolve with economic and technological development to preserve stable travel times despite increasing travel speeds. Therefore, significant decreases in future energy consumption can only be achieved by reducing the average energy used per hour of human travel.