A psycho-physical vehicle-following model tries to capture both the physical and human components of congested-traffic simulations. These models determine the reactions of the vehicle driver depending on the vehicle’s state. The state of a vehicle can be determined by the distance and by the difference in speed, in comparison to the leading vehicle. If the vehicle state changes, the driver must react. The reaction of the driver is to calculate a new value for acceleration. There are two different classical methods of time advance to calculate the state changes. This paper examines the effect of these methods on simulation run times and simulation results. Empirical experiments were done on a SLX-based simulation model.