The roads of Zone 4 cover perhaps the largest area of any of the zones. Not only are some roads in London in zone 4, but so are most of the West Midlands and Wales. It is perhaps, therefore, unsurprising that Zone 4 seems to have more long distance 4-digit A-roads than any other zone, and perhaps more B roads than any other too.
Being such a large zone, it is perhaps hardly surprising that all of the numbers from A400-A499 were allocated right at the beginning. It seems probable that a lot of the A4xxx numbers were also allocated in 1922. The biggest surprise is that Wales was treated so badly, with only the A40, A44 and A48 venturing across the border, the first two covering substantial parts of England before reaching the border.
- A4 London - Bath
- A40 London - Fishguard
- A41 London - Oakengates
- A42 Reading - Birmingham (defunct)
- A43 Oxford - Stamford
- A44 Chipping Norton - Aberystwyth
- A45 Birmingham - Ipswich
- A46 Bath - Grimsby
- A47 Birmingham - Great Yarmouth
- A48 Worcester - Carmarthen
- A49 Ross-on-Wye - Preston
The 3-digit roads covered the zone as follows in 1922:
- A400-A414 Greater London & Hertfordshire
- A415-A418 Buckinghamshire & Berkshire
- A419-A436 Oxfordshire, Warwickshire, Gloucestershire & Bristol
- A437-A443 Gloucestershire & Worcestershire
- A444-A447 Back to Warwickshire
- A448-A464 Worcestershire, Shropshire & southern Staffordshire
- A465-A474 Monmouthshire & Glamorgan
- A475-A478 Camarthenshire & Pembrokeshire
- A479-A499 Working northwards across Wales
There were, of course, many B-roads marked out in those very early years, with most of the numbers from 400-499 and 4000-4641 having been used at some stage. As with the other zones, the numbers started in London and then increased the further from the Capital they were. The original allocation seems to have run out somewhere near B4422 on Anglesey, but judging by the importance of some of the higher numbers, lots of additional routes must have been allocated right from the beginning.