If it's really cold (I assume this can happen in Scotland) it would just be grit.
(I'm not sure why "gritter" would be difficult to work out. "Grit" is a normal English word: bits of grit in the cabbage, 100 grit sandpaper.)
The UK's biggest rock salt mine is in Winsford in Cheshire https://en.wikipedia.org/wiki/Salt_in_Cheshire https://en.wikipedia.org/wiki/Winsford#Rock_salt
Additionally part of the mine is now used as a deep secure store for files from the health service.
It is important for navigation in GB. When you want to go somewhere you are supposed to use trunk roads to navigate to the first town/city on the trunk network beyond where you are going. The signs are coloured to indicate you are on the trunk network. Then as you approach your actual destination you will begin to see it signposted on the local non-trunk roads, at which point you leave the trunk roads.
This has been mostly forgotten in this age of GPS navigation, though, and many signs are in a poor state of repair or badly occluded by trees or shrubbery.
Is there somewhere I can read about this in more detail?
Thanks!
They are separated by region. So for example if you are in Cambridge (EAST region) you follow signs for EAST MIDLANDS. Once you are in that region, you will start seeing signs for the primary destinations in the region.
https://assets.publishing.service.gov.uk/government/uploads/...
Yes, this is why it is very useful to know, when navigating out of a UK town / city, the next big town / city beyond your actual destination. If you get on the correct main road, you will usually find signs to your actual destination as you get closer to it. Knowing the main road numbers (A35, etc) as opposed to their names is also really useful as is is the numbers that will be used on the signposts.
For example, you'd think about going westbound on the Piccadilly line if you wanted to get to Heathrow from Central London