Final answer:
The positions (17-99) on the brake valve are used when graduating off the brakes to achieve a gradual release of pressure and ensure a smooth deceleration of the vehicle.
Step-by-step explanation:
In the context of braking systems, the positions of the brake valve that are normally used when graduating off the brakes are represented by a range of numbers. One example of these positions is (17-99). This range indicates that the brake valve can be positioned anywhere between 17 and 99 in order to gradually release the pressure on the brakes and slow down the vehicle.
Graduating off the brakes ensures a smooth deceleration and prevents abrupt stops or jer-ky movements. By gradually releasing the pressure on the brakes, the vehicle decreases its speed in a controlled manner, allowing for a more comfortable and safe stopping process.
In summary, the positions (17-99) on the brake valve are used when graduating off the brakes to achieve a gradual release of pressure and ensure a smooth deceleration of the vehicle.