Why Train Horns? In some parts of the country, the idea of adding train horns to trucks has been around for years. In fact, there's a whole industry that has popped up offering these kits. To some, installing powerful horns on a daily driver may seem excessive, but if you're pulling a 15,000-pound trailer and you see a car about to pull in front of you, a simple warning blast can mean the difference between the driver noticing or hitting your rig.