The A3071 is a minor 'A' road in the English county of Cornwall, which links St Just to Penzance and the A30. It is 6.2 miles long.
In the early 19th-century, mines in the parish of St Just were flourishing but there were no natural harbours along the north coast. Mule trains, packhorses or wagons with four horses carried copper and tin to the harbour at the stannary town of Penzance. The wagons often grounded at the ford in the village of Hallen Tachen and a report in The West Briton newspaper on 26 May 1843 indicated that a bridge was to be built by Mr Edward Harvey of Penzance. The bridge was funded by the mining industry and Nicholas Holman who had transferred his foundry from Copperhouse, Hayle to Tregeseal in 1834. The two-span grade II listed bridge was a rebuild of an older bridge, from which the parapets and terminal refuges survive. The bridge is built of granite ashlar with granite dressings except for the rubble walls of the older bridge. The wider span is over the stream and a narrow span over the leat to Roskennals Mill. There is an inscription of "EH" on the north side and "1843" on the southern side. The village of Hallen Tachen is now known as Newbridge.
In 1863 the Penwith Turnpike Trust (later the Penzance and St Just Turnpike Trust) was formed. The road was the link between the mining region along the coast from St Just to Pendeen and carried heavy mining traffic to the harbour at the stannary town of Penzance. The Turnpike included two branches,
The turnpike provided an easier route for the teams of four horses and wagons which had replaced pack mules. A toll was charged to use the road, which was let by yearly auction. Before the turnpike was formed the mines of St Just were doing well and it was estimated that moderate tolls would raise ã800 annually. The Turnpike Act was to last 21 years from 1863 and loans of ã6,300 were advanced, including ã1750 and ã1,250 from the Bolitho and, Batten, Carne and Carne banks, respectively, with the rest from bondholders. The tolls were let for ã1000. In the late 1860s there was less traffic as mines closed, miners emigrated, and the tolls collected dropped to ã500 annually. The bond-holders did not receive any interest for a number of years around 1870 and due to falling revenue the St Just end of the road was not completed. Despite the original estimate of an income of ã800 per annum, in 1882, for example, the winning bid for running the turnpike was ã550. There was a continuation Act in 1884 and the Turnpike Trust finally closed in November 1885.
The Toll House at Tremethick Cross was put up for auction on 9 June 1886 and withdrawn by the owner Mr T S Bolitho when the ã98 reserve was not reached; the top bid was ã40.
A number of milestones and guide stones mark the route, some still surviving in their original position. They are of two designs, the earlier ones which predate the Turnpike Trust have arched tops and the ones erected by the trust have pyramidal tops. Some are listed,