I am assuming that the code assumes so to speak that the strobe is a 15 candela strobe. If you get a chance, read my other post on this issue for which I provide a lot more information of my plight. Couldn't the issue be addressed by increasing the candela level of the strobe if it is more than 15 feet from the end. Yes, safetydan, I know all about the ADA requirement. I wanted the logic behind the requirement.