Belfast·SPG008 Advertising and Signage·Page 15·4.6.2(f)
Moving or apparently moving sign elements
Signs that incorporate moving or apparently moving elements in their display, particularly where the complete message is not displayed at once, are subject to refusal on road safety grounds.
Signs which incorporate moving or apparently moving elements in their display, especially where the whole message is not displayed at one time therefore increasing the time taken to read the whole message.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/belfast/SPG008 Advertising and Signage.pdf