A raised hand combined with an arm extended sideways signals a full stop for all directions of traffic.

Arms extended forward and backward indicate that vehicles from the front and rear must come to a complete stop.

A sweeping or beckoning motion from an officer indicates you are permitted to continue forward.

When a police car activates red blue flashing lights with a rear facing STOP sign, it targets the vehicle directly behind

Flashing red and blue lights at the front of a police car mean the driver in front (you) must stop, typically for inspection or instruction.