These flashing tails came about since they pushed motorcycle manufacturers to install them STOCK on their bikes. In all reality, it gets attention faster than a normal lighted brake light. Same goes with LED tail lights. Cars/trucks could be quite different.

Most mods of this nature can be found illegal if they are not factory installed. A quick call to your state police can reveal an answer. They are usually VERY good about looking up the answer for you. I really like this mod, but I don't know if I want my car to light up like a Christmas tree everytime I stop.... especially since i live in a city. Maybe one day, I will move further out in the sticks.