Originally Posted by
gas path
Are you sure the map is immediately prewar? It shows the Colnbrook bypass and I thought that wasn't built until much later.
The bypass was 3 lanes, one each way and a take your chance suicide lane in the centre.
A4 Colnbrook bypass opened 1929. 3 lanes, 36 foot wide road was common rural main road specification from the late 1920s until 1950s. Yes, it was rural then.
Great West Road, alias the Hounslow bypass, was a little later, and dual carriageway as to urban spec.