Which would be great if the roadside extortion artist was trustworthy and had fixed prices.
Why are you so quick to trust in the goodwill and human decency of a mugger?
Not trusting in those. Trusting in laziness. $20 in the hand is a tacit promise that I won't shoot him in the back if he leaves. Anyone who has the foresight to carry "throwdown money" may also have other preparations the mugger would rather not test.
In any event, having gotten SOME money changes the dynamics of the encounter. Whether it has strengthened your position (as I hinted above) or weakened it (as in saying, "Here's the free money, but I do have more") is open to question. But it generally buys some time for you to move your other hand and your feet to a better defensive posture.
On another subject. When a mugger takes his eyes off you to pick up the dropped money from the ground you have an opportunity moment (to run, attack, reposition, etc). BUT. Some muggers will take exception to you tossing the money on the ground and consider that an insult that must be addressed with violence. Use your judgement.
Arp32 said:
A firm "sorry man, I don't have any cash" works well without unnecessarily escalating things
Saying it firmly (with the implied "FOR YOU") at the end may work for the casual panhandler and novice mugger, but unless the O.P.'s local drive-through takes credit cards, everyone knows he has at least some cash.
I suppose you could embarrass the mugger out of the crime by asking, "You SERIOUSLY want to steal my lunch money?"
To the O.P. Sorry I didn't think of this before, but did you notify the restaurant that there are people victimizing their customers in their drive-through line? The business has a VERY STRONG incentive to crime-proof their property. And they can take steps much more concentrated (on their property) than the police can.
This place may already have video surveillance in place, which could identify these guys.
Lost Sheep