Crowding effects in vehicular traffic

TL;DR

This study investigates how crowding due to car density and driving fluctuations affects vehicle transport, revealing a transition from superballistic to subdiffusive behavior and changes in distribution shapes, with implications for traffic flow understanding.

Contribution

It introduces a microscopic traffic model demonstrating how crowding causes a transition from superballistic to subdiffusive vehicle movement and alters distribution characteristics.

Findings

Crowding can induce a transition from superballistic to subdiffusive vehicle transport.

The probability distribution of vehicle positions shifts from negatively-skewed normal to exponential.

Large variability in car speeds sustains the subdiffusive state at steady conditions.

Abstract

While the impact of crowding on the diffusive transport of molecules within a cell is widely studied in biology, it has thus far been neglected in traffic systems where bulk behavior is the main concern. Here, we study the effects of crowding due to car density and driving fluctuations on the transport of vehicles. Using a microscopic model for traffic, we found that crowding can push car movement from a superballistic down to a subdiffusive state. The transition is also associated with a change in the shape of the probability distribution of positions from negatively-skewed normal to an exponential distribution. Moreover, crowding broadens the distribution of cars' trap times and cluster sizes. At steady state, the subdiffusive state persists only when there is a large variability in car speeds. We further relate our work to prior findings from random walk models of transport in cellular systems.