The California SR-41 corridor simulation project is presented as a case study of how to utilize microscopic traffic simulation for planning purposes. Two of the most important components of preparing simulation models for planning purposes are emphasized: origin-destination (O-D) matrix calibration and peak spreading for long-term testing (e.g., 20-year horizons) to overcome unrealistic network gridlock. With streamlining of the O-D calibration process, it is shown that the proposed model reproduces count and travel-time information collected from the field. Incorporating peak spreading as a result of congestion for long-term scenarios is also shown to yield performance improvements in the models and overcome network gridlock issues common to such applications.