The main roads in Northern Ireland are signed "M"/"A"/"B" as in Great Britain. Whereas the roads in Great Britain are numbered according to a zonal system, there is no available explanation for the allocation of road numbers in Northern Ireland,[1] though their numbering is separate from the system in England, Scotland and Wales.
In Northern Ireland, DfI Roads is responsible for all 25,792 kilometres (16,026 mi) of roads.[2] Road users also have the Highway Code for Northern Ireland, which provides guidance on the legal aspects of driving on Northern Ireland's roads.[3]