Blackburn's B6447 came into existence as one of the unemployment relief schemes of the 1930s, although the majority of the route is made up of pre-existing roads linked together. The route when completed became a south-western bypass avoiding the congested streets of Blackburn town centre and was also known as the 'arterial road', much like the A6119 which opened a decade earlier. Today the B6447 is a very busy road, functioning primarily as a local distributor for a town that has rapidly expanded since the completion of the route.
Branching from the A666 at the Aqueduct pub, the road heads north and immediately crosses under the Leeds and Liverpool Canal at (no surprises) an aqueduct. This structure is huge, and it is interesting to note that the River Darwen is running under the road at this point, so there are actually three levels here: canal, road, and river. Traffic is immediately pushed to the right at the mini-roundabout at the other side of the bridge, and follows urban streets before crossing under the East Lancashire line at Griffin. Had the M65 gone through the town there would have been a junction with it here, such was the importance of this road at the time.
After the railway, the road becomes Stancliffe Street, of 1938 vintage. The concrete barrier on the left stops traffic falling into the River Darwen, but was proven to be structurally unsound after severe flooding in 2002. Major repairs took until 2005 to complete and the road was reduced to one-way running for a while which caused chaos in the surrounding district of Mill Hill. This section of road could realistically have a 40 mph speed limit but it doesn't, so don't ever expect it to get one. Before too long the road becomes built up again and meets the A674 at a set of signals before climbing up towards the A677 via Buncer Lane. There are several speed cameras along this section. After bearing right onto Billinge Avenue the road terminates at the top of the hill at a mini-roundabout on the A677 Preston New Road.