[arcticbull]

Those numbers are from Bart and Caltrain's operating reports.

The Bart number may have been during peak only so fair point there, I can certainly look for the systemwide average. [1]

The Caltrain number is average over FY2016-2018, from their sustainability report page 5. [2] They completed roughly 436M passenger-miles per year, and consumed roughly 4.4M gallons of diesel. Clocks in around 100 passenger-miles per gallon. I'm sure its worse now with the COVID numbers. I think it's a fair ballpark point of comparison though, and you can consider the Bart number an upper limit.

You're of course right its a function of ridership. An average freight train gets over 400 miles per gallon per ton of cargo.

[1] https://www.bart.gov/sites/default/files/docs/GreenSheet.pdf

[2] https://www.caltrain.com/about-caltrain/sustainability