PAS, or Pedal Assist System, is a feature found on some electric bicycles (e-bikes) that automatically provides additional power to the bike's motor when the rider pedals.
The PAS system uses sensors to detect the speed and cadence (rate of pedaling) of the rider, and it adjusts the motor's output accordingly. For example, if the rider pedals faster, the PAS system may provide more power to the motor to help the rider maintain their speed. Similarly, if the rider pedals slower or stops pedaling, the PAS system may reduce or turn off the motor's power output.
For Liberty Trike riders (which are typically older or lack balance and strength), pedal-assist is more of a risk than a plus. The reason for this is that PAS (the kind that uses a cadence-sensor, as opposed to a torque-sensor), can cause unexpected lunging of the bike. Imagine coming to an intersection and naturally taking a pedal revolution on the cranks and the trike lurching forward at the exact time you are intending to come to a stop; no good. An argument could be made for a torque-sensing pedal-assist with Liberty but that would be much more complex and add significant to the cost. For this reason, Liberty Trike does not have pedal-assist but instead has a throttle-on-demand.
The throttle propulsion is further controlled by the controller programming for smooth starts from a dead stop. And you can pedal and use the throttle in any combination/ratio to effect the perfect amount of assistance while maintaining full control. In short, a throttle is more simple and safer for the typical Liberty Trike rider.
Here's a video to explain how pedaling and throttling works with Liberty Trike.
