The J Church line on Muni is still a train in part because back when they were converting lines to buses, the hill on Church St was too steep for buses.
> While many streetcar lines were converted to bus lines after World War II, the J Church avoided this due to the private right-of-way it uses to climb the steepest grades on Church Street, between 18th Street and 22nd Street.[9]
Little bit of columns A and B
https://www.opensfhistory.org/osfhcrucible/2019/08/10/the-j-...