The UK’s road numbering system feels like it was designed for the convenience of the people in Whitehall filing their maps rather than those using the roads. Giving adjacent roads very similar numbers is the maximally confusing thing to do. For my brain at least - I have to choose between the M73, M74 or M77 and I often get it wrong. It would be easier if they’d reversed all the numbers to put the zone at the end - I feel M37, M47 and M77 would be easier to remember between.