The minimum fine is $350, higher if one of those hapless "DON’T HONK" signs are nearby.Corbett says: "Make it 'if one … is nearby.'"
Fine -- but I have a different problem here: Can a sign be "hapless"? That is, "destitute of 'hap' or good fortune; unfortunate, unlucky, luckless" (OED)? Surely it's the driver who's unlucky; it would also be OK to say "if, unluckily, one of those DON'T HONK signs is nearby."
I don't mean that "hapless" can never be applied to things; "work performed on the hapless London Plane trees" is fine, since the trees are indeed having an unlucky streak. But (in my idiom, anyway) the New York sign isn't itself hapless just because its location is unlucky for some cabdriver.