How to separate gas from brake on y-axis controller

Gas is y-axis from 0 to 1. Brake is y-axis from 0 to -1. How can I tell if the brake is pressed (at the same time as the gas)? Pressing the brake just adds a negative value to the value provided by the gas pedal, so I can't distinguish between less gas or same gas + some brake. Can we map the negative y-axis to an input control, and the positive to a different one, like "LeftVertical" and "RightVertical"? If so, how is that done?