  We study the dynamics of vehicular traffic in a loop using a car-following
model with the consideration of volume exclusions. In particular, we solve the
steady state for the single-cluster case and derive fundamental diagrams,
exhibiting two branches representative of entering and leaving the jam,
respectively. By simulations we also observe that the speed average over all
vehicles reaches the same constant at the steady states, regardless of the
final clustering state. The autocorrelation functions for the overall speed
average and single vehicle speed are investigated, each revealing a robust time
scale. The effects of noises in vehicular acceleration are discussed.
