Why do car tires protect you from lightning strikes?
Category: Earth Science Published: December 14, 2012
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and Associate Professor of Physics at West Texas A&M University
Car tires do not protect you from lightning strikes. Although the rubber in a tire acts as an insulator at low voltages, the voltage in a lighting bolt is far too high to be stopped by tires or air. No matter how thick your tires are, they don't stop lightning according to physicist Martin Uman in his book "All About Lightning". Dr. Uman states that inside a car can be a safe place to wait out a lighting storm, but it's not because any materials are blocking the lightning. Rather, if the car is struck by lightning, its metal frame redirects the electrical current around the sides of the car and into the ground without touching the interior contents. The ability of a hollow conducting object to protect its interior from electrical fields and currents is one of the fundamental principles of electromagnetics. Such an object is called a Faraday cage. For this reason, riding around in a convertible, on a motorbike or on a bicycle during a lightning storm is a bad idea, no matter what kind of tires it has. If you are in a fully-enclosed metal vehicle, you should be protected from the lighting by the Faraday-cage effect. However, you should still park the vehicle and wait out the storm since a lightning strike can blow out your tires or blow out your vehicle's electronic control circuits, potentially causing you to crash if you are driving. If you are riding in a convertible or roofless vehicle, on a motorbike, or on a bicycle and are caught in a lightning storm, you should quickly seek out the nearest shelter. If a building, tunnel, or other large sheltering structure is not readily available, seek out a low point in the terrain away from water, away from isolated trees, and away from other tall structures (e.g. windmills, power-line towers).