Mass Car Ownership
After the First World War, there was a gradual increase in motor-car ownership, although this was to a certain extent retarded by the inter-war years of depression. Nevertheless, more and more commercial carriers embraced the internal combustion engine and by the mid-1920s, it became clear that unless checked, traffic congestion intowns could become a problem in the future. This was particularly apposite in old settlements such as Blackburn, with narrow, winding streets, totally incapable of coping with large flows of traffic. In many respects, this is a problem which has never gone away.
The government began to get to grips with Britain's road problem in the early 1920s by classifiying roads according to their function. Long distance trunk and primary routes became A-roads, urban and rural cross-routes becoming B-roads. Minor streets and lanes remained unclassified. Former turnpike roads usually became A-roads. The main routes serving Blackburn and Darwen were the A666 (former turnpike to Bolton and Manchester) and the A59 (the Preston to Skipton turnpike). The main roads to Burnley and East Lancashire became the A678 and A679. Roads were numbered according to the 'zone' in which they began. Therefore, A-roads beginning with a number 6 started west of the main A6 trunk road.