When you need to brake, how can you warn drivers behind you?

Question

To warn drivers behind you that you are about to slow down, it may be a good idea to first lightly tap your brake pedal a few times to make the brake lights flash.

Accepted Answer

Tap on the brakes a couple of times.

Answer

Stick your arm out the window.

Answer

Swerve within your lane.

Answer

Change lanes.