Because of the low Bridge in Chiswick DDs (when it went via Acton Green) have never gone on the 440. But TfL do like to send double deckers on rail replacement along the 440 route between Acton and North Acton.
But presumably the rail replacement buses don't go around North Acton Playing Fields. I'm sceptical a DD could easily do those turns, happy to be proven wrong though
No they don’t they just go straight down Noel Road.