Muni Trivia: Name This Mystery Gauge Thing

Photo by @Shanna

Shanna asks on Twitter: “Any idea what this is measuring? Found it under the seat on Muni.”

We had no idea either, until we asked our Muni driver friend, who has an answer for us. “This is a measure for how much sand is left in the bags on the Light Rail Vehicles. The LRVs use a lot of sand on rainy days or for hard braking.”

The LRVs carry sand under the seats and drops sand onto the tracks for traction on rainy days or for hard braking in other situations.

One mystery solved.


  • DevinMcCutchen

    This is one of those funny little things that has carried through a century of trolley design. It’s probably just a basic conservation of space issue, but the sand reservoirs of many older trolley cars are also located under the seats. If you look near the base of any steep track grades in the city, say the spot where the J hits Dolores Park, you’ll often see a lot of sand right around the rails.

  • Virgil Dennis

    Typical Muni attention to useless details; who cares between 3/4 full and 1/4 full? Look at the glass and if you see sand you’re OK, if you don’t see sand…you need sand.

  • kittens

    Sand? I always thought they were full of rice! But srsly take a closer look- it’s totally rice

  • Dexter Wong

    There’s many different kinds of sand, some fine, some coarse. It’s probably some kind of coarse sand in the dispenser.

  • Jeremy

    You can hear and feel the train sliding on sand when it comes to a quick stop. That’s the sliding sound you hear right after the blow their horn. Otherwise the metal on metal stops way too quickly and deforms the rails/wheels.

  • Roger

    What type of horns do the new Muni lrv street cars use?

  • Riley

    “Name This Mystery Gauge Thing”.

    Uh, Sandy?

  • Henry Larry

    It is intriguing how even the most mundane objects can hold such interesting functions. Kudos to Shanna for the curious question and to the Muni driver friend for unraveling the mystery.
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