Comment by fraserharris

This article is somewhat out-of-date. The L & 7 trains were modernized to communications-based train control (CBTC) & automatic train operation (ATO) since 2006 & 2018 respectively. This allows for moving-block signaling, where a trains are separated by a distance, instead of fixed blocks of track. The legacy fixed-block signaling system is still retained as a fallback.