Something you may or may not know about the Orange Line when it is closed for Assembly Square construction

Ever wondered why the northbound train is just sitting there for heaven knows how long at North Station on the nights and weekends that the Orange Line is down for Assembly Square construction between Sullivan and Oak Grove? Well, the reason is because they are running single rail operation between Sullivan and North Station. They do not clearly mention this on the website, maybe because they assume everyone knows this, but I don't think everyone does. And the only crossover on the tracks in that stretch is right before the tunnel between Community College and North Station. Therefore they HAVE to run single rail if they are to turn a train around without going to Wellington. So when you see an announcement on mbta.com about Assembly Square construction on a given night or weekend, don't just prepare for the sardine cans that pass as shuttle buses, but also intense delays outbound at North Station waiting for a train to get back to North Station on the single rail stretch to Sullivan.