The road measures 23.75 miles long and would take a car obeying speed limits 56 minutes to travel its length.
The A666 is a A Road and is located in the Zone 6 Highways Region.
This is a true long-distance route, journeying through numerous towns like DARWEN, BLACKBURN, Egerton, BOLTON, Farnworth, Wilpshire, Langho, Swinton, and Kearsley.
The road connects Lancashire and Greater Manchester.