During a trip, you can find buttons named "Tap to lock vehicle" and "Tap to unlock vehicle" available for use in the Beam app. Use these features to temporarily lock and unlock your Beam vehicles as necessary.
For example, when you need a toilet break during a ride, park your vehicle at a safe place and use "Tap to lock vehicle" in the Beam app to prevent other riders from using it. When you return to the Beam vehicle, open the Beam app and use "Tap to unlock vehicle" to unlock the Beam vehicle and continue riding to your destination.
However, note that throughout the duration your Beam vehicle is locked, you will still be charged for every minutes for occupying the Beam vehicle. If you have any active Ride Pass or subscription, the benefits will be utilised instead.