CTA train lights identify route
A commenter on this post (about telling the difference between a Purple and Brown Line train) reminded me about how lights on the front of a train tell you which line it is.
So I went to the ultimate source on all things about the Chicago El: http://www.chicago-l.org/
Of course there's an exhaustive article on the issue. But here's a screenshot from the site that summarizes the markers for each line:

Also, the Pink Line uses White-Red, which hasn't been added to that list.
Posted by: Matt | October 18, 2006 at 07:09 AM
Wish I knew this on Monday when I got on a Red Line train thinking it was a Purple Line.
Posted by: Tovi | October 18, 2006 at 08:31 AM
This is a little too complicated. I wish they would just put up some kind of sign on the train indicating the line and the final stop.
Posted by: Adam Kotsko | October 18, 2006 at 03:31 PM
Adam, technically they do, but sometimes the signs are wrong. If in doubt, ask the operator in the first car.
Posted by: Tim | October 18, 2006 at 03:55 PM
"I wish they would just put up some kind of sign on the train indicating the line and the final stop."
Adam -
They do. There is one sign on each side of every car. The color reflects the name of the line, while the text indicates the destination.
It's really simple, and easy for anyone to understand.
Posted by: huh | October 18, 2006 at 05:56 PM
I thought it would be obvious that my previous comment was intended as a joke. I apologize for the apparent misunderstanding.
Posted by: Adam Kotsko | October 18, 2006 at 09:21 PM
Adam -
You're right. It should have been obvious. (Probably was to everyone else.) However I let my frustration with other inaccurate and unsupported posts in other threads blind me. I should have realized, given your posting history, that you were knowledgeable about basic signage and were speaking tongue-in-cheek. Mea culpa.
Posted by: huh (duh) | October 19, 2006 at 02:11 AM
The main reason I use them is you can see them at MUCH further of a distance away (especially at night). So, if you are trying to figure out whether to come out from under the heater/platform to brave the rain/cold to get to the car you like, it helps to be able to do it before the train is stopping.
The only slightly tough ones are telling the difference between a red and purple line at a distance as they come from the south. The white lights aren't pure white, and the headlights tend to obscure them a bit.
I mostly ride on the North side, so I don't know how useful they are at other places with multiple trains. I have used the lights in the Loop to tell whether a train at a previous station is my train. I also wish they had the lights on the back of the train as well so I could tell if I just missed my train or another line.
Posted by: Flynn | October 19, 2006 at 11:15 AM
who cares about the lights....just board any train and go in which ever direction it takes you! (notice my free spirited attitude)
Posted by: cmama | October 19, 2006 at 11:50 AM
I have no idea how to read these lights. If I want to take the purple line from Howard to Belmont, what lights will be turned on? White/White? If I want to take the same line to Howard? Yellow/Red?
Posted by: Tovi | October 20, 2006 at 09:50 PM