4 Digits (42xx)
| Road | From | To | Notes |
|---|---|---|---|
| B4200 | Wednesbury, West Midlands | A4038 near Darlaston, West Midlands | |
| B4201 | A4117 near Cleobury Mortimer, Shropshire | B4363 near Cleobury Mortimer, Shropshire | |
| B4202 | A443 at Abberley, Worcestershire | A4117 near Cleobury Mortimer, Shropshire | |
| B4203 | A443 at Great Witley, Worcestershire | A44 at Bromyard, Herefordshire | |
| B4204 | A443 at Worcester | A4112 at Tenbury Wells, Worcestershire | |
| B4206 | A443 at Worcester | A449 at Worcester | |
| B4210 | Walsall, West Midlands | A462 near Essington, Staffordshire | |
| B4214 | A438 at Ledbury, Herefordshire | A4117 at Cleehill, Shropshire | 28 miles long |
| B4217 | Five Ways, Birmingham | A4040 Fox Hollies Road at Acocks Green, Birmingham | Route of the number 1 bus |
| B4221 | B4215 at Newent | A40 at Ross-on-Wye | |
| B4223 | A4058 at Llwynypia | A4061 near Treorchy | |
| B4230 | A438 near Byford | A4112 near Weobley | By way of Mansell Gamage, Norton Canon and Weobley |
| B4233 | Abergavenny | Monmouth | By way of Llanvapley and Rockfield |
| B4237 | A48 at Newport | A48 at Newport | Now the former A48 route through Newport. The previous route, including Newport Transporter Bridge is now unclassified. |
| B4242 | A4109 at Aberdulais | Pontneddfechan | |
| B4245 | A48 at Llandevaud | A48 at Caldicot | |
| B4260 | A40 near Bridstow | A40 near Hildersley, Ross-on-Wye | |
| B4265 | A4226 near Cardiff International Airport | A473 at Bridgend | |
| B4271 | A4118 near Upper Killay | B4295 at Llanrhidian | |
| B4275 | A4054 at Abercynon | A4059 at Penywaun | Originally the A4059 route. |
| B4278 | A4093 near Gilfach Goch | A4058 near Dinas | This road originally ran through Dinas and Tonypandy but was upgraded to the A4058 route. |
| B4278 | A4058 near Porth | A4233 near Stanleytown A4058 near Llwynypia |
This road was originally the A4233 and A4058 but following the completion of the Porth Relief road these roads were downgraded. |
| B4280 | A473 near Pencoed | A4061 at Bryncethin | |
| B4282 | A4017 at Cwmafan | A4063 at Cwmfelin | |
| B4283 | A48 near Groes, Port Talbot | A4229 at South Cornelly | |
| B4284 | Five Ways, Birmingham | B4124 in Edgbaston, Birmingham | |
| B4286 | A4241 at Port Talbot | B4287 at Pontrhydyfen | |
| B4287 | B4434 at Neath | A4107 at Pontrhydyfen | |
| B4290 | B4489 at Swansea railway station | A4067 at Victoria Park | |
| B4290 | A483 near Jersey Marine | A4230 at Neath Abbey | |
| B4291 | A48/A4230 near Peniel Green | B4603 at Clydach | |
| B4295 | A4216 at Cockett | B4271 at Llanrhidian | north Gower road |
| B4296 | A4118 at Killay | A48 at Pontarddulais | |
| B4297 | A484 near Bynea | A4138 near Llangennech | |
| B4298 | A40 west of Carmarthen | B4299 at Meidrim | |
| B4299 | A4066 at St Clears | B4333 south of Newcastle Emlyn | by way of Trelech |
Read more about this topic: B Roads In Zone 4 Of The Great Britain Numbering Scheme