How does Google Maps compute ETA?

Focus on the algorithms and data sources that Google Maps uses to calculate Estimated Time of Arrival (ETA). Discuss the role of real-time traffic data, historical traffic patterns, and geographic information in the computation process. Highlight how machine learning models may be employed to predict travel times based on various factors such as time of day, weather conditions, and road closures. Additionally, consider mentioning how user-generated data contributes to improving ETA accuracy over time.