I cut a perfect .400 light on a Pro Tree years ago at the old Fremont drag strip in the San Franscico bay area foot braking in S/St That was when they(NHRA) were still using conventional bulbs in the tree and I saw the pre stage and stage light flicker a little bit before the three yellows all came on at once, I was sure I red lighted but once I figure out what had happen all my Pro lights got a lot better