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B roads are numbered routes in Great Britain of lesser importance than 
A road
A roads may be
*motorways or freeways, usually where the local word for motorway begins with A (for example, ''Autobahn'' in German; ''Autostrada'' in Italian).
* main roads or highways, in a system where roads are graded A, B and sometimes lower c ...
s. See the article Great Britain road numbering scheme for the rationale behind the numbers allocated.
3 digits
4 digits (40xx)
4 digits (41xx)
4 digits (42xx)
4 digits (43xx)
4 digits (44xx)
4 digits (45xx)
4 digits (46xx)
References
{{DEFAULTSORT:B Roads in Zone 4 of the Great Britain Numbering Scheme 4 4