What is reactive braking?

Answer 1

This applies to electric or gas/diesel-electric vehicles. An electric motor can be instantly converted to an electric generator when polarities are switched. So, when you want your electric car to slow down or stop, you could have the motor suddenly turn into a generator. If the generator has very high electromagnetic flux, then it will act as a brake, and the kinetic energy of the vehicle is converted into electric charge in the battery.

Hence, reactive braking actually "saves" the kinetic energy for future use. Gravity Reactive Braking involves using a special ratchet for wheelchairs and stationary machinery, in which the kinetic energy is rapidly converted into potential energy; the basic principle is similar to a steep ramp, used to slow down a rolling cart.

Sometimes "reactive" braking means the brake system is mechanically designed to engage under certain conditions, such as excessive RPM.