Don't think for a moment I won't drive with you on my hood and brake sudden enough to throw you off into the car in front. And if traffic speeds up while you're on there, not only are you physically fucked but I'm reporting you as an attempted carjacking.
It really depends on the situation, sometimes you'll have people who drive into the pullover lanes and skip as many people as they can and they expect you to automatically let them in.
I just put mine on a 2008 explorer, I stuck mine in behind the front bumper, there is just enough metal it gets a great resonance and will make people jump, especially in the local town that has had main street destroyed four times in 30 years by runaway semi trucks.
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