I went looking in to the flash modes. On the Nite Riders it looks like the flash modes are intended for daytime use.

On the Metro I used there was a flash mode I ran at night on the road that "twinkled" in an intermittent pulse. It was enough movement it would draw attention, but it wasn't a full on/off "flash" that I found hard to keep my eyes adjusted to at night.

So far the only Nite Rider I can find that has a potential "night flash mode" is the Lumina Pro 1300 where it has a pulse flash, but it appears a full deep on/off when it flickers - way more than a "twinkle".