This means that the tire's reinforced sidewalls are capable of supporting the weight of the vehicle and the passengers in case of air pressure loss for 50 miles up to the speed of 50 mph. As a result, the driver is not stranded on the side of the road if the tire gets punctured. Instead, they can safely drive to a nearby location where they can fix or change the damaged tire. Run flat tires are usually made for vehicles without space for a spare tire. They cannot be mixed with regular tires as their structure is heavier.