TLRN

A London-specific term, standing for the "Transport for London Road Network" (alternatively, the "Transport for London Route Network").

Transport for London (TfL) is responsible for a specifc set of roads in London. In practice this means most A and some B roads, although many 'main' roads will be administered by the London boroughs and not by TfL.

A map of the TLRN is available here.