I thought they were daft!, they were infact running above houses
and as someone who live near the elevated part of the M4 I can assure you its not that nice (also helps disperse pollutants?
Oh yeah, completely mad, but at least the designers were trying to think about the issues of car ownership, and vehicular access to cities, and that at a time when private car ownership was very much lower than now, so they were pretty prescient.
Loved the Victorian structures, a bugger keeping the pigeons off all those decorative bits, though. 😀
And having driven over the M4 elevated on many occasions, I feel your pain.
Still, nice views of Wembly stadium, and the Audi West showroom. 😉