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Recently a friend and I were offroading in the local mountains and while ascending a trail a storm blew in. We were out in the open near the top of the mountain when lightning started. We weren't sure if we would be safe inside our vehicles so we stopped and got out and moved away from them. After talking a few minutes some other people came down from the other side of the mountain and we decided to follow them back down.

Did we make the right decision regarding exiting the vehicles and moving away from them? Or is it safer to stay inside your vehicle during a lightning storm?

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    Does this provide an answer to your question?
    – Benedikt Bauer
    Jul 11, 2014 at 17:40
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    Were you out in the open, or were there many tall trees around?
    – Chris Mendez
    Jul 11, 2014 at 17:46

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It is safer to be inside the vehicle than out. The NOAA National Weather Service's lightning safety page recommends vehicles as a safe location during a thunderstorm:

You are not safe anywhere outside. Run to a safe building or vehicle when you first hear thunder, see lightning or observe dark threatening clouds developing overhead. Stay inside until 30 minutes after you hear the last clap of thunder. Do not shelter under trees.

This is also covered on a couple other Stack Exchange sites:

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No, you should definitely have stayed in your vehicle.

Think about what lightning will do. It is attracted to tall conductive things, but that's not the whole story. A vehicle on a flat plane is more likely to be hit, but the conductive metal on the outside will shunt the current around the contents of the vehicle. It may be very loud and unpleasant, but the metal box around you will protect you from the lightning currents.

If you are outside, either you're close to the vehicle or your far away. If close and you can get low, then the lightning is more likely to hit the vehicle than you, but you are still in danger from ground currents and possible arcing from the vehicle's metal frame thru you to ground. If you are far away, the vehicle is irrelevant and you're outside in the open in the thuderstorm. Not good either.

The above advice is base on the assumption that the vehicle is a full metal cage around you. If it has no top or a plastic (not conductive top), then you're not inside a cage and the protection the vehicle provides is not as good. In that case, I'd try to get as low as possible on the floor below the seats. You want the lightning to hit the metal frame instead of you directly inside the vehicle.

In the case I was in this situation in a convertable with a canvas top, for example, I'd put the top up and get as low as possible onto the floor of the car. The top will mostly make it more comfortable by keeping the rain off you, and might provide just a little bit of shunting should lighting hit the vehicle. Wet canvas is still more conductive than air, but nowhere near as conductive as a steel frame.

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    Can the lightning ignite the gas tank and start a fire?
    – Extreme Coders
    Jul 13, 2014 at 5:38
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    @Extr: Pretty unlikely. The air space in the tank above the gas is too rich to ignite. The tank itself is usually metal or has metal around it, so lightning wouldn't go thru it anyway. If there is a small fuel leak by the engine, then lightning sparking all around could ignite the vapors. However, that's all less likely than you get hurt due to lightning by being outside the car.
    – Olin Lathrop
    Jul 13, 2014 at 19:27
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Yes. It is safe to be in your car when in a lightning storm.

Cars (pretty sure not soft-tops) and planes act as a Faraday Cage

Faraday cages are metal containers or meshes which protects against static and non static electricity.

As a note... Top Gear also tested this in laboratory conditions with an artificial lightning generator and Richard Hammond inside the car. This is the YouTube for: Richard Hammond gets struck by lightning Top Gear

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If your vehicle has a closed metallic structure, you are definitely safer inside than out: if lightning strikes your vehicle, or near your vehicle, the metal will conduct the electricity away from you. The protection is almost as good as if you were inside a building with a lightning rod.

If you are in an open-top vehicle, or one with a non-conductive roof, things change: in an open-top vehicle, your head is one of the highest things around, while lightning striking a non-conductive roof is likely to burn through and strike you. In that case, I'd exit the vehicle and take whatever "outside in a thunderstorm" precautions are appropriate for your location.

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