A Flash Alert is triggered by an absence of any green phases for longer than 10 seconds. In pedestrian scenarios that use an All Pedestrian interval, the Walk signal can be quite short followed by a longer Don't Walk signal. If the All Pedestrian Don't Walk period is greater than 10 seconds, that implies there are no green phases for long enough to trigger a Flash Alert. Depending on how phases (channels) are assigned, and/or how the TS1 harness is wired for that cabinet type, there are other valid scenarios that could cause an apparent loss of greens for more than 10 seconds and trigger a Flash Alert.
In these situations, the Flash Alert should not be added to the configuration.