Nova Scotia’s Public Utilities and Board of Review invoked the stop clause at midnight Tuesday, citing what it called “significant changes in the purchase price of gasoline.” Motorists in Halifax were paying at least $1,804 a liter for regular gas on Monday. The new regulated minimum price for natural gas in Halifax is now $1.734 per litre. That’s a drop of seven cents per litre. The price of diesel was not affected. The regular weekly fuel price adjustment comes on Friday.