I was at Disney during a RunDisney weekend but I wasn’t participating in the race.
I had heard horror stories about road closures and traffic delays to Magic Kingdom, so I was a little worried, but… it all went really well!
I had the most magical day.
Now I’m sharing my experience for future liners who might find themselves - accidentally or not - trying to get to Magic Kingdom on half marathon day.
The single most important thing you want to do is to take the first bus to magic kingdom!!
Do NOT take rideshare, do not drive yourself, no MinnieVans either.
The is no direct access to Magic Kingdom. Everyone goes to TTC. The walking pathways will be closed too.
The ONLY way to get to MK is by monorail.
My experience
The first bus was scheduled to leave the resort 1 hour before early entry (7:30 am for an 8:30 am)
=> 7:25 am: The first bus leaves CSR.
The driver warned us it would be a much longer trip. He said: “you may want to use the bathroom… we don’t know how long we will be in traffic .
I think we were on World Drive getting closer to TTC, and this is the interesting part: It seems only Disney buses were allowed to continue towards MK.
Cars had to get a separate lane and turn left to who knows where…? This is my understanding of the situation, but if anybody else knows more about this - please comment.
This is SO COOL! We saw the runners from the bus!! This was a new experience for me. And now I want to intentionally go to MK on a race day to cheer for total strangers!
It just looks like they were pushing cars towards the Mulan/Ursula part of the TTC lot, and then having them work their way forward. Possibly towards the heroes side. The buses are going down the villains side and then under Seven Seas drive to the TTC entrance/security area.
Do NOT take rideshare, do not drive yourself, no MinnieVans either. 
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