This is the answer, but there’s a far easier number to memorize.

“#77”

That number, on any “State-owned primary roadways in Maryland” will contact an MDOT dispatcher who will send out help to your location.

They’re absolutely lovely, and made my tire getting destroyed by a pothole not the worst. :)

edited to add: for free. The attempt to reinflate my tire and put on a spare was 100% free.