I think i have read anything one day about that.....
Another way is considering that in every bus stop have some delay,
Another is, considering time in route, example, the route that result is the route that takes less time to take, because every time you go down bus, and up to the other you should wait some time. every stop has a waiting time.
If the problem is only length , then i don't know. Network analist count barriers , i don't know how, maybbe a function or vba script, have seen many doc's about that but without source code