You might want to up the flash rate to ~4/second. The DOT regulation specifically states 240 cycles /minute ±40.
Additionally you should (must per reg) have a daylight sensor to kill it for night use...
Well, I like the 1Hz better (although it is adjustable up to 4Hz. I think)- it matches what the buses use exactly and is less annoying. The buses run the strobe at night, too. Obviously, you can't modulate a headlight at night, since it would affect your ability to see the road in front! But the strobe won't matter, since it is not the primary light source.
I think what I propose might be in the spirit of the law, if not the letter. Besides, the slower rate makes it that much more obvious it is not an emergency vehicle. At the current brightness of it, I am not sure how effective it would be. It is nowhere near as bright as those blinding bus ones.