It's called the red line. If you are taking the train between 5pm and 6pm on a weekday, you need to prepare yourself for the ride from hell. It's not horrible all the time, but when you hear that dreaded announcement "We are experiencing minor/major delays due to a disabled train at fill in the blank station", you know it is going to be a shit show trying to get on that train.
When the train finally rolls up and the doors open up, you know you're about to get really friendly with all the people on that train. People are already squished like sardines in the cart, but what's a few more people? You're literally fighting for your life getting on that train. You may need to use an elbow or two, but no matter what you have to get on there because you don;t no how much longer it will be for another one. (Even though it's usually only a few minutes or so). A little advice, try and get as far in to the train as possible so at the next stop you don't get thrown around by the people rushing out.
As soon as you think you can't possible fit more bodies in this cart, there is always that one asshole who starts yelling at everyone to push in so he can get on. It's actually hilarious trying to watch some people morph their bodies in crazy ways to fit in the train before the doors shut. It's even funnies watching the doors shut and everyone yelling and pushing the person off the train so we can get moving. Honestly this is just another Tuesday night coming home from Boston.