Contributor

And maybe not eat the day before.
According to
WaPo, 5,000 portable toilets will be made available to visitors at the Mall and along the parade route. The newest estimate for crowds on January 20 is between 500,000 and 1.5 million.
To my limited math skills, in the best-case scenario there will be 1 potty per 100 people and in the worst case, 1 for every 300. That's a really long line to pee.
According to the article, there is actually a toilet-to-bladder recommendation! To a commercial provider of potties 1-to-100 is a good recommendation (of course, they're renting them), while the National Parks Service says 1-to-300 should be adequate, so it looks like the planning for evacuation is well within known limits. Of course there are caveats for weather. I don't know about you, but I tend to have to go more when I'm cold.
But alas, I will not be going. I don't like standing in the cold, crowds and portable toilets. I'll watch the festivities from my warm house where the ratio of humans-to-toilets will be 3-to-2.