This map shows the ----------------new route.
1)bus
2)buses
3)bus'
4)bus's
5)either 3 or 4
Both 3 and 4 are acceptable. My preference would be #4.
For me, bus's and ONLY bus's.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.