Route 340 begins at Notre Dame Junction, which is a nickname given to the route's
interchange with
Route 1 (the
Trans-Canada Highway). Leading northward, the route passes through the town of Lewisporte, where it then continues by turning right at an
intersection with
Route 341. The route continues northeastward and passes through the shoreline communities of
Michael's Harbour and
Campbellton, where the route intersects
Route 343. Continuing northeastward, the route also intersects Route 331. This route leads to ferries connecting Change Islands and Fogo Island with the main island. Route 340 then passes through the community of
Boyd's Cove. Afterwards, the route leads northward through a series of
causeways that connect the main island of Newfoundland with New World Island. While on New World Island, the route passes through the town of Summerford and intersects
Route 344. Following that intersection, the route leads northward until passing through
Virgin Arm, where it then intersects
Route 345 and leads northeastward. It then passes by
Dildo Run Provincial Park and through the communities of
Fairbanks,
Hillgrade and
Newville. 1.5 km north of Newville, the route intersects
Route 346 and then veers westward towards a
causeway connecting New World Island to Twillingate Islands. After the causeway, the route immediately veers northward and passes through
Purcell's Harbour and
Little Harbour, where the route then veers northwestward. The route then passes through the town of Twillingate, where a left turn at a local intersection is required to remain on the route. Through the town, the route is largely residential and is called
Main Street. After a small loop, the route leads northwestward through
Tickle Bridge and continues through Twillingate. The road then passes through
Wild Cove and
Crow Head, where a sharp right turn is required to remain on Route 340. The final stretch leads northward to
Long Point Lighthouse, located at the edge of the
Atlantic Ocean. == List of communities along route ==