Conventions - Source of USRN
7.3.3.1
One USRN must be recorded for each on or off slip Road.
7.3.3.2
One USRN must be recorded for each link Road for each direction of travel.
7.3.3.3
USRNs for slip Roads must be taken from the LHA USRN range.
7.3.3.4
Motorway interchange junctions, primarily roundabouts, should be included as ESUs of the main carriageway which they serve. In most cases this is a main ‘A’ Road or Trunk Road. Special cases exist where a roundabout must be included as an entity of the main carriageway.
7.3.3.5
If a roundabout serving a Motorway is officially named, this section of the Highway must be recorded as a USRN.