We didn't realize so small a percentage of rush-hour trains are 8-car consists. That actually helps us to understand why we see a lot of the (separate issue of) complaints of not enough cars on the system for rush hour, thank you for enlightening us!

When we raised the HVAC issue with WMATA, we wanted to try and get a handle on why so many people were consistently complaining about it.

Unfortunately, we weren't dealing with our usual contacts from the MetroAccess side of WMATA, so only got the pseudo-boilerplate response we quoted here instead of the detailed ones we usually get.

From Glenn Millis' original reply to us, we're led to believe that the HVAC systems in each car are independent and a closed system, which in theory wouldn't affect the HVAC in the rest of the consist (I think?).

We're still unable to say if the driver has any control over HVAC operation on their trains – I don't suppose you know anything about this (or know someone who does?) so we can eliminate that as a possibility?

We tried to emphasize from the start that our analysis was based on the numbers alone, without taking into account variables that we can't quantify – the biggest being no idea how many cars with HVAC issues are taken out of service rather than deployed. So we know more information coming in will help us refine the analysis.

From the perspective of people with disabilities, that 1-in-6 or 1-in-8 chance of getting a car with HVAC issues is kind of important – there are practical issues that traditionally limit the cars available to us – though I'll admit in many cases they're not "barriers" per se.

It's not very easy for many people with disabilities to switch cars at a station, for example – Once we're in a car, we're pretty much there for the duration. Likewise, for some people (for example some blind riders) the familiarity issue kicks in – it may be important for their "memory" of their route to use the same car each time.

So the 4% number, or 0.04% chance measured against the entire rolling stock, whilst small (and, in all probability, not able to be reduced practically), still brings it to a level that people in the community need to be aware of (and, maybe gives able-bodied riders more information than they had before on this issue to boot).

We did try to qualify the basis of the analysis as best we could and pointed out it didn't take into account practicality and real-world issues. I can see how the resulting data from pure math alone may seem to be unfair, but I'd hope those qualifiers would bring the results into some perspective for the readers.

We're not really trying to question their numbers specifically (though we have a reputation for demolishing their MetroAccess statistics on a regular basis), more trying to get a better handle on the issue's prominence in the feeds and on the 'net in general.

With Conditional Eligibility looming, we want to try and find the answers to things people with disabilities may have heard about but don't understand and get answers – and if we find issues that we think may become problems down the line, try to raise them with WMATA in time to resolve them before they blow up.

HVAC implies heating as well as a/c. Most people are well bundled up in the winter and my sense is that heating problems are under-reported. My 600+ rides per hot season says I'm either:
-very- unlucky OR
my tendency to board the same position of car in the train is increasing my personal odds OR
I'm not going to get another hot commute this summer (as I'm well over the 4% of 600 to date) OR
the numbers Metro has are not accurate.

First, only about 25% of rush-hour trains are run as 8-car consists. That increases the number of trains created with 1100 railcars. The total number of trains run peaks in rush hour at about 120-125, or around 850 railcars, so you’re not too far off there.

Second, unless one car without AC can affect the other cars in the same train somehow, it’s unfair to inflate the numbers by implying there’s a problem if any car in a train has a problem. Yes, you might have a 30% chance of getting on a train with at least one car with HVAC problems, but in that train you have a 1 in 6 or a 1 in 8 chance of being in the car with HVAC problems, which is the same 4% that Metro quoted.