Just like Zone 5 to the west, the huge length of Zone 6 makes it appear to be one of the larger zones. It is, but for all its length, it is never particularly wide, and covers some sparsely populated areas such as the Pennines, Northumbria/Cumbria border and Southern Scotland. Heading south, Nottinghamshire is where the A1 and A6 start to converge as they approach London, squeezing Zone 6 to nothing in the process.
At first glance, Zone 6 should have easily used up all of it's A6xx numbers as it strides north, but at the southern end a lot of Zone 4 and Zone 5 numbers cross the A6, reducing the number of A6xx roads that were used. Fortunately, the vast urban areas of northern England helped redress the balance.
- A6 London - Carlisle
- A60 Loughborough - Doncaster
- A61 Derby - Thirsk
- A62 Manchester - Leeds
- A63 Leeds - Hull
- A64 Leeds - Scarborough
- A65 Leeds - Kendal
- A66 Penrith - Hull
- A67 Bowes - Stockton on Tees
- A68 Darlington - Lauder
- A69 Carlisle - Newcastle upon Tyne
The 3-digit roads covered the zone as follows in 1922:
- A600-A605 Greater London - Peterborough
- A606-A624 Nottinghamshire, Derbyshire & southern Yorkshire (Sheffield)
- A625-A637 Southern Yorkshire
- A638-A661 Western Yorkshire (Leeds & Bradford)
- A662-A683 Eastern Lancashire (inc Manchester)
- A684-A697 Northern Yorkshire, Durham & Northumberland
- A698-A699 Southern Scotland & Northumberland
There were, of course, many B-roads marked out in those very early years, with most of the numbers from 600-699 and 6000-6482, and another block of 65xx numbers having been used at some stage. As with the other zones, the numbers briefly started in London and then increased the further from the Capital they were. The original allocation seems to have run out somewhere near B6373 near Edinburgh, but judging by the importance of some of the higher numbers, lots of additional routes must have been allocated right from the beginning.