It is important that vehicles without space for a spare tire have run flat tires mounted on them, as in the case of a puncture or other air pressure loss, the driver will not be stranded at the side of the road. Instead, they will be able to get to a safe destination where they can change or repair the tire. Run flat tires are heavier than regular tires, as their sidewalls are reinforced to support the weight of the vehicle and the passengers. Due to the difference in weight, regular tires and run flat tires cannot be used together on the same vehicle.