B roads are numbered routes in Great Britain of lesser importance than A roads. See the article

Great Britain road numbering scheme In Great Britain, there is a numbering scheme used to Categorization, classify and identify all roads. Each road is given a single letter (representing a category) and a subsequent number (between one and four digits). Though this scheme was in ...

for the rationale behind the numbers allocated.

B300 to B399

B3000 to B3099

B3100 to B3199

B3200 to B3299

B3300 to B3399

B3400 to B3499

B3500 to B3999

Footnotes

References

{{DEFAULTSORT:B Roads In Zone 3 Of The Great Britain Numbering Scheme 3 3