Notice that:
1.- The first route takes 2 hrs and 30 min from your town to Detroit.
2..- The second route takes 2 hrs and 45 min from your town to Detroit.
3.- The third route takes 2 hrs and 30 min from your town to Detroit..
4.- The fourth route takes 2 hrs from your town to Detroit..
Answer: Route 4 takes the least amount of time.