The eastern terminus of Trunk 3 on provincial maps is at the Armdale Roundabout in Halifax.

Traveling outbound from the traffic circle Trunk 3 formally proceeds west using the name St. Margaret's Bay Road and passes through Timberlea and Upper Tantallon.

West of Chester, Trunk 3 follows the shore of Mahone Bay to reach the town of the same name.

Trunk 3 is no longer signed in some portions between Bridgewater and Barrington, as Highway 103 assumed some of its former route in the 1970s.

Trunk 3 "re-appears" as the main street and approaches to some towns that Highway 103 has bypassed, including the Liverpool, Lockeport and Shelburne areas.