Whatever happened to all the accellerometer - based brake flashers that were out there? They have all disappeared from the web and marketplace in the last few years. The only one out there right now is the one made for Miatas by MX5things. G-Stop and the few on amazon are permanently out of stock, and on the company web pages they have simply vanished. It's not a legal issue that I can tell, since several manufacturers use Emergency Safety Signal systems that flash the brake lights, hazard lights, or both upon sudden deceleration.

I'm thinking I'll have to roll my own at this point. Basic accellerometer ICs aren't terribly expensive, and a PICMicro or PicAxe should be complicated enough to run things. Something like 0G-.3G normal brake lights, .3G-.6G 3 1sec flashes then steady, >.6G three 1/2 sec flashes then steady.

Thoughts? Or info on where these products actually went? What the issues were, legal or otherwise? I haven't been able to find anything on a NHTSA or Fed-DOT ruling, letter, etc. saying they were disallowed at a federal level. Motorcycles still use them.

 

I know for a fact that it is illegal to make your brake lights flash, no matter how "cool" you think it is.
I have seen lots of people with brand new cars that are having these installed on the 3rd brake light. I don't get it, for some amount of time, when your brake light should be on, it is off, and possibly off when a distracted drivers just takes a quick glance upward from their phone screen.

On some emergency vehicles, I have seen where the brakes lights have 2 stage brightness, bright and super-bright. Under sudden braking the brake lights come on with a pulsation from bright-super bright to grab attention WITHOUT having an OFF period of light. I would bet that this is totally legal as the light output never falls below the minimum requirements. Lights that flash are technically below minimum light output for some period of time.

If you are going to make something custom, try and make something smarter than the off-on flasher, maybe the bright-super bright pulser.

 

So you are correct in that you cannot have a continually flashing red/brake light. Momentary flashing is not - otherwise, someone pumping the brakes (for us pre-ABS people) would be illegal. Most states don't have laws on pulsing the brake light or if there are a number of flashes that are OK - but some do (usually 4) and the manufacturers are bringing out systems that do this. Mazda, Hyundai, Mercedes and BMW.

Supposedly (I can't find my source link at the moment) in California the devices are legal – so long as the brake lights flash no more than four times within four seconds.

I'm not going after a cool factor here - I want to flash the brakes lights 3 times (about 1x per second) when I brake fairly hard, and 3 times much faster when I brake at the limits. This is to get attention to the fact that I'm stopping rapidly - because where I live, the G37 is a small car and I almost regularly have near-misses when someone panic brakes in front of me and I follow suit.

I'm considering building a flasher that uses an accelerometer to determine how hard I'm braking and flash (or not) accordingly.