Looked but didn't see

[freeflow]

It's why I prefer pink/magenta/red for cycling. Particularly if it's a bit misty.

[Pastychomper]

Although behind me was a predominantly man-made backdrop (buildings and asphalt), might that yellow/green have been mistaken for a privet bush (or similar)? Does the brain process green as a stationary colour? That's the colour that the human brain has experienced most during its evolution, and it is generally associated with objects planted firmly in the ground (parakeets notwithstanding).

Is there any science behind the hi-vis industry, or is it all founded on common sense?

As I understand it there is at least some science behind it, though I don't know if it goes as as far as that. Human eyes are most sensitive to the yellow part of the spectrum, so a yellow jacket will look brighter than a blue one if they reflect the same amount of light. Red and green, being close to yellow, are also highly visible - hence their use in traffic lights and (presumably) the pink, orange and greenish hi-vises.

A complicating factor is that something like one in ten UK men have trouble distinguishing between red, yellow and green, so they'd see any common high vis against a hedge as a brighter patch of background. I don't know if that gets taken into account when designing these things.

[peetee]

I seem to remember hearing that Hi-viz in some situations is creating the opposite effect. The argument went along the lines that when going about your business in an area where high viz is common the brain expects to see the colour so effectively ignores it and injury is often the result. Creating a similar scenario for nefarious means, criminals have got away with theft from building sites and railways for many years now by looking the part by going high viz to 'blend in' and be ignored.