This article is a follow-on to How Slow Is The 510 Spadina Car? and an update of The Gradual Slowing of 512 St. Clair (Parts 1, 2 and 3).

Like the Spadina route, St. Clair operates in a reserved lane with many farside stops. The route has also been through the transition from CLRVs to Flexitys, and is subject to many of the same operational rules as the Spadina car. However, there are a few significant differences: St. Clair has fewer intersections (special track work) where slow orders apply, and the transit priority signalling is supposed to be active except at major intersections where cross-street capacity takes precedence.

The charts here are in the same format as those shown in the previous Spadina article for ease of comparison.