What is the difference between the "controlled braking" and "stab braking" methods for an emergency stop?

Explanation

Controlled braking means applying the brakes as hard as possible without locking the wheels, keeping steering movements small, and releasing and reapplying if a larger correction is needed or the wheels do lock; stab braking means applying the brakes all the way, releasing completely the instant the wheels lock, and reapplying at full force the moment the wheels catch traction again, which can take up to a second. 49 CFR 383.111(b)(7)(iii) directly requires CDL applicants to know emergency stop procedures, and these are the two named methods the manual teaches for that knowledge area. Neither method is tied to a specific road surface; both are available on any surface depending on the situation, so limiting one to wet roads and the other to dry roads is wrong. Continuous rapid pumping without a full release describes neither method correctly, since stab braking specifically requires a complete release when the wheels lock, not a partial pump. Assigning controlled braking to the parking brake and stab braking to the service brake is wrong because both methods use the service brake pedal; the parking brake is not part of either emergency stop technique.

Source: 49 CFR 383.111(b)(7)(iii)