rolling ATM machine
A personal car or motorcycle that is much cheaper to run than the rate at which mileage is reimbursed for work use. (the current government rate is $0.50/mi, other places do $0.40/mi, etc.).
Nick: I work for the Census and ride my 1980 Honda Cub. I get reimbursed fifty cents a mile but it costs six or seven cents a mile to run.
Hamal: That's like a rolling ATM machine!
Hamal: That's like a rolling ATM machine!