The Traffic Light System was introduced by the Department for Energy and Climate Change (DECC) and was announced in a Written Ministerial Statement of 13 December 2012 (https://www.gov.uk/government/news/written-ministerial-statement-by-edward-davey-exploration-for-shale-gas).
It was adopted on the advice of three independent scientists who conducted an expert review of information available following seismic events at Preese Hall near Blackpool. The independent Oil and Gas Authority are now the regulatory body responsible for monitoring induced seismicity at hydraulic fracturing sites.
The expert review recommended that operations should be paused if an event was detected above a precautionary threshold of a magnitude 0.5 but did not specify a pause period. Before hydraulic fracturing operations can commence, a Hydraulic Fracture Plan must be agreed between the operator and regulators and a minimum pause of 18 hours is required following an event above this threshold. This pause period has been in place for all hydraulic fracture plans so far and has been applied during the regulation of operations at Preston New Road.