Microscopic traffic simulation models are applied in the analysis of transportation systems for years. Nevertheless, calibration (and validation) of microscopic sub-models such as car-following and gapacceptance models is still a recent matter. The objective of the calibration is to adapt the simulation output to empirical data by adjusting the model’s parameters. However, simulation results may vary from the underlying real-world data, despite the calibration. To analyze these deviations the present paper compares two different approaches of calibration using data from a single-lane car-following experiment on a Japanese test track. It is demonstrated that the results of the two methods differ significantly. A recommendation for the more appropriate method to use is given.