The control cables on your vehicle brake system are a secondary line of protection to prevent unwanted motion or tire rotation. Parking brakes are often employed when automobiles are parked in precarious positions with regard to elevation, when towing things, when needing to do bodywork, or to change a tire.
If your vehicle is in need of new control cables, you may notice a lack of tension when you apply the emergency brake. Because of the safety elements associated with the brake system, it is never wise to pursue brake maintenance as a last resort. Check the condition of your cables, and act as necessary.