Why do studies find that the net benefits of bus transportation are less than those of cars?

1. Your friend is giddy about their new commute strategy. He says that if he leaves 30 minutes earlier for work, he avoids major traffic on the interstate and his commute time is cut in half. An economist walks in and declares that your friend is still costing himself with this new strategy. Explain why the economist is right or wrong. (one paragraph)
2.  Why do studies find that the net benefits of bus transportation are less than those of cars? (one paragraph)
3.  Does expanding highways (adding lanes) under a come as you please system result in reduced congestion in the long run? Why or why not? (one paragraph)