https://mutcd.fhwa.dot.gov/resources/interim_approval/ia21/index.htm
New approval. Somehow they worked out a way to get around the proprietary nature of the RRFB patent holder. For now. (He kept patenting more and more flash patterns.) We'll see what happens next.
Sucks that everyone has to reapply for the new interim approval, per the revised FAQ (https://mutcd.fhwa.dot.gov/resources/interim_approval/ia21/faq/index.htm)
Quote from: Alps on March 20, 2018, 08:26:01 PM
Somehow they worked out a way to get around the proprietary nature of the RRFB patent holder.
The text of IA-21 addresses this, under FHWA Evaluation of Results:
QuoteThe FHWA has confirmed that the patents on the RRFB device that was the subject of Interim Approval 11 have been expressly abandoned and the concept of the RRFB is now in the public domain. Because of this action, the RRFB is once again eligible for interim approval status and the FHWA is issuing this new Interim Approval for the RRFB.
Also interesting: The flash pattern is different in the new interim approval. The old pattern (2 slow flashes on left, 3 or 4 quick flashes on right) is no longer allowed. The new approved pattern is the more recent "left, right, left, right, together, together" that had been allowed via a later official interpretation. Existing RRFB installations under the old interim approval have to be reprogrammed to the new flash pattern when units are serviced or replaced.