Petrol rationing was introduced in September 1939 with an allowance of approximately 200 miles of motoring per month. The coupons issued related to a car's calculated RAC horsepower and that horsepower's nominal fuel consumption. From July 1942 until June 1945, the basic ration was suspended completely, with essential-user coupons being issued only to those with official sanction. In June 1945, the basic ration was restored to allow about 150 miles per month; this was increased in August 1945 to allow about 180 miles per month.