Sorry for the delay in responding.
Using 2011 and 2013 as the times around the 2012 RSR debut, TSMM wait times averaged ~3 minutes lower after RSR opened. My stats guy says that's not statistically significant over the course of an entire year though.
Here's the chart:
Sure. And it's quite possible/likely that a similar phenomena would occur at DHS if additional rides are added -- rather than cause wait times to go down at TSMM, the additional guests (or guests that stay longer in the park) might keep the wait times similar. In which case, you are back to the capacity issue, which is what the third track is trying to solve.
You're also comparing very different environments with multiple variables.. and drawing conclusions about one of them. That is horribly wrong.
For starters...
DCA isn't strapped for attraction capacity... DHS is
DCA isn't strapped for the kid demographic... DHS is
DCA's TSMM was not extremely overloaded (high waits)... DHS is.
Carsland significantly boosted overall park attendance - that means you need to account for that increased load
Attractions are not necessarily equal for demand pull - especially if they require significantly more investment. Ex: RSR is a 60+min wait regularlly.. TSMM was 30-40min typically. Takes more 'investment' to goto RSR instead of TSMM.. that eats at how much canabalizing of demand there is too.
DCA was quite balanced - DHS (still) is not.
The uptake on available capacity is is not necessarily a linear function. The further you get into deficits for supply, the more desperate people will get and tolerate more waits. The more surplus there is, the tolerance for wait will not track linearly with supply necessarily.
It's nice to say 'if there is a new attraction eating 1200/hr - that will reduce the count waiting on other attractions by that much' - but the world isn't that pristine and pure. But what we do know is DHS is in a severe deficit of desirable attractions for people.. so if you add something compatible, and desirable, it should help siphon load off.
People do not like to wait for attractions at 100+mins.. when normally the expectation is more like 15-30mins. That is an additional variable that would make it easier for people to float to an alternative attraction if it were compatible and desirable.
The comparison between TSMM on both coasts is an interesting one. Using it as an example is a very valid metric that can be applied to both understanding the parks (and the resorts they are in) on each coast.
For this discussion, we will use the word "popular" to define attractions that can pull guests into line for it.
When discussing either coast, you need to get the obvious facts off the table. TSMM is "popular" because it is a fun, interactive, attraction. In Disney parlance - a solid D+ to E ticket attraction. It's interactive, it's competitive, and that translates into being fun.
When you discuss "popularity" or lines at theme parks, you are really having a discussion of supply vs. demand. A lot of this discussion in this thread has been focused on the supply part - which is the "pph (people per hour)" function of the attraction.
TSMM is also an attraction that provides very marginal hourly capacity by Disney standards (800 - 1200pph).
Demand is the part of the discussion where the real heart of the matter is.
Demand for TSMM is different on either coast.
TSMM at DCA is a metric of a "popular" attraction at a now healthy park.
TSMM at DHS is a metric of a "popular" attraction at a very sick park.
The demand part of the equation in determining "popularity" aka length of lines is really determined by factoring all the other alternatives that the park the attraction is in has to offer. Think of the real sum of an attraction's popularity as being something as vain as a popularity contest. Attractions vie for a guests attention the moment they step through the gate. What determines the length of the line for a specific attraction is how many guests opt to get in line (physically or virtually) over every other attraction that is available.
TSMM at DCA has a plethora of "worthy" attractions that pull guests away from it.
TSMM at DHS has next to nothing to serve as the pull.
This "pull" is the proverbial magnetism attractions have over guest decision making.
Using the attached graph for DCA TSMM's wait times before and after RSR came online shouldn't be a surprise. TSMM had the same amount of pull on guest behavior as it did before even though overall park attendance went up. It's important to note, that DCA's redo was really to effect the "popularity" of the overall park. It was designed to serve as the magnetic pull to draw guests away from DL and hold them at DCA. The increase in attendance has been absorbed by the growth that Carsland/Mermaid/and WoC added.
If you understand how attractions pull guests into its lines and the impact that has not only to the health of a park; but, the overall resort - then TDO's move of adding a 3rd track to TSMM at DHS at this point in time is disturbing.
The "pull" will likely remain the same.
The current issue at DHS isn't that TSMM is pulling guests into its line over ToT, RnRC, or ST. The current issue is what guests are pulled to AFTER they complete those attractions.
That pull will still likely mean hopping over to another park and that means likely hopping to MK.
The "unhealthy" nature of DHS isn't that TSMM is "popular". The unhealthy nature is that DHS can't keep people occupied for an entire day.
Allowing 1/3 more guests to notch their belts with a TSMM ride quicker will do nothing more than add to the overall problems with the resort. Until TDO recognizes that the solution to this problem is to bring enough compelling attractions online to keep guests satisfied at the current park they visit, then the grass (artificial as it may be at the Hub) will always be greener on the other side of the imaginary Magic Band gates.
The real benefit of a 3rd TSMM track won't be felt until DHS has enough online to keep guest happy for an entire day. If Star Wars Land comes and doesn't bring enough native capacity on its own to offset the increase in attendance, it will be very messy.