Crowding Effects in Vehicular Traffic

Jay Samuel L. Combinido, May T. Lim

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 a 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.