In this paper, we present a full velocity difference model for a car-follow
ing theory based on the previous models in the literature. To our knowledge
, the model is an improvement over the previous ones theoretically, because
it considers more aspects in car-following process than others. This point
is verified by numerical simulation. Then we investigate the property of t
he model using both analytic and numerical methods, and find that the model
can describe the phase transition of traffic flow and estimate the evoluti
on of traffic congestion.