The design just looks a bit gash. It's using a Lilypad, which is meant to be used for wearables, but given the quite moderate demands made on IO by the design it's far too large. I would have used something like an Arduino Mini, or Teensy, or something even smaller if it exists.
As others have said, the chevrons are essentially a waste of time, from even a moderate distance, a driver will not be able to see the individual elements, it will just be a yellow light. The usefulness of a flashing light or a moving object (ie a hand or arm) is also arguable, and I think I'd just go for a solid yellow light that came on when held in the appropriate location.
9 times out of 10, a retroflective is going to be at least as efficient, a lot cheap, and much more easily replaceable when it eventually wears out (after a year or two).