I know SSR doesn't share buses, but does that also mean each park at DTD is only given one bus? Because a round trip from SSR to MK is almost an hour, which would be much longer than the standard "20min" wait. I would think that's ridiculous!
I think I understand your question and like most people, due to the complexity of the WDW bus system, you have a misconception on how it works. It would take me pages and pages to explain how the buses are dispatched at different times of the day but the short answer, specific to your question is, NO.
Buses are not assigned a specific route which they continue to do all day long. A bus driver may not even do the same resort more than once in a work day.
Buses are assigned their next resort as they return to their origination point or Hub (Think Park). This keeps the buses moving at an even rate to all resorts and continuosly corrects any problems, such as traffic, mechanical issues, weather, accidents, etc., that may have occured on a previous buses trip to that resort.
Due to Disney's improvements to their system over the years and with the addition, 3 weeks ago, of 40 new buses, wait times are rarely more than 15 minutes. No system is perfect and their will be the rare exceptions to the rule. For example, just yesterday, due to heavy rains, the tunnel near the CO flooded and buses, along with all other traffic, were forced to reroute around the back of MK, causing very long delays.
Just some food for thought. WDW has 18 resorts which are serviced by over 330 buses. This means that there are over 18 buses serving each resort at any given moment.
OT - Here are a couple of tips to make your bus riding experience better.
- Never leave right after fireworks
- Never leave when it starts to rain
- Give yourself plenty of time (1 1/2 hours) when travel from resort to resort
- If you have a question about the buses, ask a bus driver. Don't ask a monorail or boat person and vis-a-versa
- And the biggest tip of all. Don't estimate how long you have been waiting for a bus. Look at your watch when you arrive at the bus stop. If you do that you will be surprised at how short your waits really are.