According to Wikipedia, (1), the Portway is the name of the Roman road running “running from London to Weymouth, via Silchester (Calleva Atrebatum), Salisbury/Old Sarum (Sorviodunum) and Dorchester (Durnovaria).” The road leads towards Porton, which was presumably named after the Portway.
‘The Portway’ is the name given both to the path that runs along the south of Old Sarum, as pictured below, and the road that leads from the Beehive roundabout on towards Porton.
I would imagine that this is historically correct, but a bit confusing.
The Portway, Stratford
[...] think it is part, or possibly a continuation, of The Portway, which is the Roman road which connected Dorchester to [...]
[...] was next to a busy crossroads in Roman times – the major road, the Portway, running from London to Dorchester and Exeter, meeting a road to [...]