List of Michigan County-Designated Highways - Zone System

Zone System

As implemented in October 1970, the CDH system is divided into eight zones: six in the Lower Peninsula and two in the Upper Peninsula. This contrasts to the state highway system that makes no attempt to group designations by geography in the state. The boundaries for each zone are determined by major state trunkline highways on each peninsula. Each highway is given a designation composed of the zone letter followed by a two-digit number. Within the zone, numbers are assigned on a grid system: north–south highways use odd numbers and east–west highways have even numbers. Lower numbers are used to the south or west sides of the zones.

The Lower Peninsula is divided into six zones, A-F:

• The A zone is bordered by I-96 on the north and US 127 on the east.
• The B zone is bordered by I-96 on the south, US 10 on the north and US 127 on the east.
• The C zone is bordered by US 10 on the south and both I-75 and US 127 on the east.
• The D zone is bordered by US 127 on the west and I-96 on the north.
• The E zone is bordered by US 127 on the west, I-96 on the south and US 10 on the north. As of 2012, no highways have been designated in the E zone.
• The F Zone is bordered by both I-75 and US 127 on the west and US 10 on the south.
• The Upper Peninsula is divided into the G and H zones. The dividing line between the two zones is US 41, between Lakes Michigan and Superior with zone G lying west of US 41 and zone H lying east of it.