NRM stands for NAASRA Roughness Meter Counts.
Prior to the introduction of modern laser profilers many Australian Road Authorities captured ride quality / road roughness data in NAASRA Roughness Meter Counts (NRM) which was related to the vertical movement of a rear axle of a standard vehicle. A vertical movement of 15.2 mm amounted to one NRM.
The NRM system has been largely replaced by the IRI system.
Old NRM roughness data can be converted to IRI via the following formula.
IRI = (NRM + 1.27)/26.49