If you're driving along and suddenly lose air pressure in one of your tires, it's likely that you've been punctured. There are a few telltale signs that can clue you in to this problem. First, if you hear a loud popping noise when the tire goes flat, that's a good indication that it's been punctured. Additionally, if you see a small hole in the side of the tire, that's another sign that something has pierced the tire and caused it to go flat.
If you think you may have a punctured tire, it's important to pull over as soon as possible and assess the situation. It's not safe to drive on a flat tire, so if you can't fix the problem right away, you'll need to call for a tow truck or otherwise get your car off the road. Once your car is safely parked, take a close look at all four tires to see if any of them show signs of being punctured. If so, then it's time to change out the tire for a spare or call roadside assistance for help.