Fundamental diagram of vibration-driven vehicles

In this study, we conducted experimental investigations into the fundamental diagram of vibration-driven vehicles (VDV) in a one-dimensional array. As these mechanical agents interact solely through collisions, their mean speed remains nearly constant at low and medium densities. However, there is a reduction of between 25% and 40% when the lineal density approaches the inverse of the contact distance. Remarkably, in this one-dimensional system, the outcome is significantly influenced by the order in which agents, sorted by their free speeds, are gradually introduced into the experiment. While a significant speed difference is observed at low and medium densities based on this ordering, both curves eventually converge to the same speed at maximum density. Moreover, the attained speed in saturated systems is slower than the speed of the slowest agent.