I’m glad you’ve reconsidered your use; but with the Transportation Secretary suggesting a similar thing today, well, the road to you-know-where is paved with good intentions.
When you go through any sort of FCC licensing, you learn a lot about why the FCC is so conservative. When you’re emitting RF, the law of unintended consequences is in full effect.
In this case, you’re not only dropping the calls of your fellow drivers. You’re also dropping calls for every pedestrian, house, office, and business you drive past. You also probably drive by a lot of cell towers every day without realizing it. And depending on conditions, that advertised 100 feet could be 10 feet, or it could be half a mile.
Even if you magically limited the interference to cars, you’re also killing passengers’ calls and emergency systems like OnStar.
Besides (and this may be anathema here), I think there are some legit reasons to make a call while you’re driving – reporting a drunk driver, or calling 911 in a situation where you don’t feel safe stopping.