The Humber loop was close to where the old border of city of Toronto was. Same
reason why the 40 Junction terminates at Runnymede, it was the old border of the
city of Toronto.

The Humber loop is obsolete now. The only reason for it is that the 66A Prince
Edward southern terminal is at the Humber Loop, while the 66D terminates at
Marine Parade Drive passing the Park Lawn Loop. The 80 Queensway no longer
terminates at the Humber loop, but continues to Parkside Drive and up to the
Keele station.