For civic-addressing purposes (such as 911), nearly all rural roads in Perth County are numbered.
The roads maintained by the County are numbered in accordance with this scheme; for example, "Perth Line 9" is the section of Line 9 that the county maintains, and "Perth Road 151" is the section of Road 151 that the county maintains.
Reference: Minutillo, Carmine.
Backroad mapbook, Southwestern Ontario, second edition.
Perth County Road Map, Perth County Planning and Development Department, 2012