This document summarizes a case study on Apollo, an open source self-driving car system. The study examined how machine learning models are used and integrated within Apollo's codebase. It found that Apollo relies on multiple ML models from different frameworks as inputs to other models, making integration complex. The models are configurable and interconnected, with code providing safety checks on outputs. While ML-related code executes frequently, test coverage for this code in Apollo could be improved according to the study.