What algorithm does Google Maps use?

I'm curious to know, could you elaborate on the algorithm that Google Maps utilizes to deliver such precise and efficient routing services? I'm particularly interested in understanding the intricacies of how it calculates the shortest or fastest routes, as well as how it handles real-time traffic data and updates. Is it a proprietary algorithm developed in-house by Google, or is it based on existing mathematical models or frameworks? Additionally, how does the algorithm factor in user preferences and customizations, such as avoiding toll roads or highways? Lastly, could you provide any insights into the potential challenges or limitations of the current algorithm, and how Google might be looking to improve or evolve it in the future?