The figures are in, and they're not so impressive.
DC Metro has released ridership figures for the weekend. Look on that page for most of the raw figures below.
September 12, 2009 - Rail ridership: 437,624 Bus ridership: 236,347
(I sum that to 673,971 total trips)
That is well lower than average workday rail/bus ridership (which is over one million: 700,000 rail and 450,000 bus on most weekdays).
But let's compare the Saturday of 9/12 to Saturday one week earlier:
September 05, 2009 - Rail ridership: 300,963 Bus ridership: 236,347 [see note at bottom]
(Sums to 537,310 total trips)
So, this past Saturday was about 26% above the previous Saturday's rail ridership. Bus ridership was the same both weeks [see footnote]. Teabag day didn't even come close to ridership levels for a regular weekday with commuters.
There were about 137,000 extra trips (that would include both to and from trips) the past Saturday over the previous one, meaning probably around 68,500 excess round trips on the subway this weekend compared to last. I wouldn't attribute all that transit to the TeaBag event, and one would have to figure in the people who drove, but that seems in line with official estimates of around 60-70 thousand protestors on Friday. Also, there were other events that same Saturday 9/12 (American triathlon and Black Family Reunion), so ridership would have been up for them, too.
However, it's apparent there was no huge ridership surge on Saturday that would have come from more than 100,000 protestors.
Let's compare ridership with Inauguration day:
January 20, 2009 - Rail ridership: 1,120,000 Bus ridership: 423,000
About 800 thousand more trips for Obama's inauguration than on last Saturday.
To throw in a weekend day for a comparison without weekday workers, how about the Sunday two days before inauguration?
January 18, 2009 - Rail ridership: 616,324 Bus ridership: 152,108
So, even the Sunday two days before inauguration had more ridership (especially by rail, but even by rail and bus combined) than the teabaggers had on Saturday.
I wonder what university Beck got his figures from?
---"footnotes"
* I realize Metro gives the same figures for bus ridership on both Saturdays 9/5 and 9/12. I'm presuming that's an artifact of how they do their routing and not an indication that the number of trips were precisely the same -- still it's the figure they give for both days.
Disclaimer: I don't live in DC and can't be sure how the Metro reports their figures-- I simply used what is on their reporting page.
Same post at my blog http://riffle.blogspot.com/, which I'm more likely to update if needed.
++++
UPDATE:
I should reemphasize that the National Black Family Reunion likely drew quite a crowd. From their website: "The Black Family Reunion Celebration (BFRC) is a three-day cultural event that is recognized as the largest, most significant family event in the nation, attracting more than 500,000 people each year!" That's their estimate of over 500,000 and it's over 3 days, but it's quite a few regardless.
Also: Jethrock and others note that Armey and Beck bused in a lot of people, which is true. But there were a lot of buses for Obama's inauguration, too.
This is by no means a way of getting a precise count, but it does show that estimates over 100 k visitors are profoundly off the mark.