St. Austell is the largest town in Cornwall.
As with most of the larger Cornish towns, St Austell now sports a bypass, taking through traffic away from the town centre. However, back in 1957 the A391 and A3061 still met in the middle, the A3061 possibly taking over a former alignment of the A390 route. To the west of the town, the A3058 heads off to Newquay, and remains virtually unchanged fifty years later.
This map also seems to erroneously label the B3274 as the B3374, however this is correct as the B3374 used to reach St Austell, its route partially robbed by the realigned A391. To confuse everyone, that roads old route is now part of an extended B3274.