Since the city's light-rail vehicles are heavier than a BART car, the term "light rail" is something of a misnomer. The air comfort systems on these Muni trams contain more than two dozen separate electric motors. They are not rudimentary vehicles.
And yet, the miracle substance preventing our hulking, intricate trains from speeding off out-of-control is remarkably low-tech: sand. Without a steady supply of the stuff disgorged from within the trains and trolleys onto the tracks, metal wheels will not stop upon metal tracks. The substance that makes Silicon Valley go also makes trains halt.
As such, Muni's five steel-wheel divisions run through prodigious amounts of sand, ordered from an outfit in Monterey in 30-pound sacks at a rate of 17 cents a pound. The city's historic cable cars dumped 50 tons of sand onto the street last year — alas, the sand is not reusable. That's four times as much sand as the jaunty Italian-made streetcars spat out, but only half as much as the light-rail vehicles housed at Muni's biggest car barn. All told, 256 tons of sand was used last year in preventing trains from running into one another.
Putting this into context, 256 tons of sand would fill a 50-by-25 meter Olympic-sized pool to the depth of one meter — halfway to the top.
That would bring a swim meet to a screeching halt — not unlike a Muni train.