For you California flashers:

http://www.dmv.ca.gov/pubs/hdbk/pgs41thru4...mergencysignals


Use Your Emergency Signals

If you can see an accident ahead, warn the drivers behind you by turning on your emergency flashers or tapping your brake pedal quickly three or four times. You can also use the hand signal when slowing and stopping.

Never stop on the road, unless necessary for safety or to obey a law. If you need to stop, then start braking early as a signal to the cars behind you.
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Personally I use the "brake tapping" thing quite a lot (for situations that don't necessarily warrant the hazard flasher but still you'd like to try and get the attention of the person behind you).

Nice forum you have here btw - just stopped by researching the cupholders for a friend who picked up a 525 last night.. think the UCII might do it.

 

I used to drive a lot in Mexico and I remember seeing incoming traffic (Especially truck drivers, buses) flash you twice with their high beams when there was a speed tramp ahead (A federale or a Highway Patrol). That was very helpful.
I have not seen that in the US though,

I agree with the flashers thing and I do it every time I think is appropriate

 

Ooooo Tap my brakes? I need all the breaking power I can get... forget tapping... Flashers will do. I usually do a gradual slow to a stop so if the guy behind isnt paying attention and is still speeding up I can release the brake and give him more room. I think if I want to use the tap the brake technique I need to practice that... Else I wont have enough stopping power left for myself