Screamscape is reporting that due to construction of Tron, the railroad will be closing for a time period, as will the Speedway. Not sure of exact dates of this at this point…but those planning trips in the coming months through early 2019 might want to plan accordingly.
I had read earlier that the exit for Space Mountain has been temporarily diverted. Is this still the case?
Yes, the exit for Space Mountain is still diverted.
While I was there last week I spoke with a cast member who stated the railroad is closing for 3 years. I guess that pretty much means Tron is going to open fall 2021.
Tron opens in 2021, yes. But I have doubts that the Train would be closed that long. I imagine they will spend effort first either diverting the train, or building a new tunnel for the train that they can build Tron over. But if the train is closed for 3 years, that’s pretty significant.
Concept art shows the training going smack dab through the middle of the Tron coaster area, so I don’t think they will be diverting the train unless they do so only temporarily.
Another interesting rumor that has some credence behind it is that the Speedway will be updated to be TRON-like, possibly with futuristic electrified vehicles instead of gas-powered, etc. If this is true, it is long overdue, since NOTHING about the Tomorrowland Speedway today makes it seem like it belongs in Tomorrowland! Instead, it makes it seem like it belongs in “Yesteryearland”. 
Ohhhh, that would be AWESOME if they do that to the speedway!!
My 16 year old rode it 3 times last Friday and said it needed an update. (And he is a young man of few words. He rode it to practice driving in anticipation of his first driving lesson next week!)
As far as the train closure, I actually heard it from thee sources, that are not connected. One was our vip tour guide, and the other two both work in Resort and park development. Maybe they are closing the train until Tron opens to avoid looky-Loos taking photos/video and posting on social media?
I’m so excited for Tron though. 2021 is a big birthday for me and it falls in October as well. Already trying to decide our dates, and if we are staying on or off property. I’ve been doing both this year, and I equally enjoy both experiences.
So many new and exciting things out there!!
When is the railroad closing?
Exact date hasn’t been announced, though some sources are saying December 2018.
After my visit so no worries here!
fwiw the tp refurbishment schedule appears to have it listed as down from Dec 18 - Summer 19
Lance over at Screamscape has a pretty solid track record. If he was uncertain, you can be sure that it would be marked RUMOR:
Not saying he can’t be wrong, but his accuracy on stuff that he reports as news is pretty high.
Yes, I was pretty upset about the closure as it starts before my visit. I had plans for that train. 
Yep, the plan is to update the Speedway to the Light Cycles. However, look what happened to the Theatre before you get carried away!
The imminent closure to the Speedway however is just for the preparation work for the Tron ride. The update to Speedway should happen later on, nearer to 2021.
Our visit starts December 2nd…I’m hoping the train runs the first week, at least…I know my girls would love it!
They didn’t name a date, so it may still be open. I’m there the last week of December, so I’m pretty sure that it will be closed by then.
I’m crossing my fingers, too! (Our trip starts Dec 1.) The Disneyland train was down my last two visits there. I need a train ride!
There is a train in AK. 
Yes, there is a train at AK, but it doesn’t take you to various areas of the park in order to avoid the bottleneck that is Main Street…