Ought a green citizen to bicycle or take public transport to work?

We theoretically study whether an environmentally conscious or “green” citizen ought to bicycle or take public transport to work. Focusing on the criterion of travel time minimization, we construct and analyze a simple stochastic model that sheds light on the above question. Our investigation leads to three findings. First, we compute the expected amount of time it takes to commute to work. Second, we derive a key inequality condition and show that only two cases need to be considered to determine whether a green citizen ought to bicycle or take public transport to work. Finally, we provide an intuitive explanation of why it suffices to consider only two cases to answer the question in the title of this note.