The yellow sleeper brought to mind my thought why does so much of the rail system look like a linear scrap yard? [Duck!]
If nothing else all the old rails have to have some scrap value? Not to mention bags of ballast that have been there that long the bags have rotted, etc. etc.
End of moan
Network Rail has continuous campaign, and occasional purges, about lineside scrap, including unused materials (as well as others for litter, vegetation, etc.). Rail is the main concern, as
this promotional presentation from 2016 makes clear. As its last slide says: "Scrap not only looks unsightly. It hurts people and it damages infrastructure."
The background is that, of course, moving materials out to a work site and back afterwards adds to the cost, and - most importantly - extends the possession time. Hence deliveries are done in advance, and carefully scheduled (with its team), and e.g. new rail is often left near or on the track. Removing stuff afterwards can be done any time, so it tends to be put off because something else is more urgent or the team (or budget) can't all be found. But I'm sure this used to be even worse a few years ago.