Without the randomization step (third action), the model is a deterministic algorithm, i.e., the cars always move in a set pattern once the original state of the road is set. With randomization this is not the case, as it is on a real road with human drivers. Randomization has the effect of rounding off an otherwise sharp transition. Just below this transition, one car braking due to a random slow can slow down the cars behind, spontaneously creating a jam. This feature of one car braking at random and causing a jam is absent in a deterministic model.