The strengthened structure maintains the ideal tire shape under the pressure in case of air pressure loss. Once air pressure leaves the tire, due to punctures or other damage, the reinforced structure enables the tire to be driven on for 50 miles up to 50 mph. This limited, temporary performance prevents the vehicle from being stranded on the side of the road. These tires are designed for vehicles without space for a spare tire. Also, run flat tires cannot be mounted together with regular tires on the same vehicle.