  The data presented here show that human drivers apply a discrete noisy
control mechanism to drive their vehicle. A car-following model built on these
observations, together with some physical limitations (crash-freeness,
acceleration), led to non-Gaussian probability distributions in the speed
difference and distance which are in good agreement with empirical data. All
model parameters have a clear physical meaning and can be measured. Despite its
apparent complexity, this model is simple to understand and might serve as a
starting point to develop even quantitatively correct models.
