This document outlines BusMezzoDynamic, a dynamic transit modeling tool that simulates traffic conditions, transit operations, and passenger route choices. The model has several components: (1) a mesoscopic traffic simulation, (2) modeling of transit operations and uncertainties, and (3) modeling of passenger demand and dynamic route choices. It is intended to evaluate impacts of transit operations strategies and real-time traveler information provision. A case study of the Stockholm metro system demonstrates how the model can simulate passenger route choices and travel times under normal operations and service disruptions with and without real-time information. Ongoing work aims to further develop transit operations strategies and the passenger choice-set generation model.