Cash in the Car
Ever since the gas price scare that followed hurricane Katrina I have kept $50 in smaller bills in the glove compartment of our vehicles, as an emergency fund to make sure we could both get home should some other outlandish even occur.
My daughters car laid down on her and it cost $80 to get it towed. Bummer. And gas continues to hover about $4 a gallon, so I figure I need to up the ante to about $100. That's enough for gas, towing, a meal, possibly a hotel room or even a co-pay at the ER. And all in small bills. Gas stations may not change a large bill late at night.
Yes your credit/debit card should work, but in a wide area emergency that may not be the case. And every body accepts cash.