Public transportation plays a critical role in people's daily life. It has been proven that public transportation is more environmentally sustainable, e cient, and economical than any other forms of travel [3,15]. However, due to the increasing expansion of transportation networks and more complex travel situations, people are having di culties in e ciently nding the most preferred route from one place to another through public transportation systems. To this end, in this paper, we present Polestar, a data-driven engine for intelligent and e cient public transportation routing. Specically, we rst propose a novel Public Transportation Graph (PTG) to model public transportation system in terms of various travel costs, such as time or distance. en, we introduce a general route search algorithm coupled with an e cient station binding method for e cient route candidate generation. A er that, we propose a two-pass route candidate ranking module to capture user preferences under dynamic travel situations. Finally, experiments on two real-world data sets demonstrate the advantages of Polestar in terms of both e ciency and e ectiveness. Indeed, in early 2019, Polestar has been deployed on Baidu Maps, one of the world's largest map services. To date, Polestar is servicing over 330 cities, answers over a hundred millions of queries each day, and achieves substantial improvement of user click ratio.