single tracking

Does CTA subway trains can support single tracking running both directions on the same track when the other track is down on all lines ?

Single-tracking does occur periodically in the Red and Blue line subways during certain maintenance windows, but it's normally done very late at night, when the intervals between trains are longer, in order to minimize disruptions. Also, Red line trains are rerouted via the Loop elevated (otherwise known as "running over the top") whenever both tracks in the subway are closed for cleaning. This is normally done early AM on Sundays...

It's done on the L tracks as well, and it sucks! I've missed more South Shore trains downtown due to L trains being late from the near north side.