Wikipedia:WikiProject Canada Roads/Prince Edward Island/Notes on numbering and notability

The network is way too dense for every route to be notable. Three digit routes are essentially numbered by county: Prince County 1, Queens County 2, and Kings County 3.

Two-digit routes are:

Route 1, Borden to Wood Islands
Route 1A, Albany to Travellers Rest, formerly also to St. Eleanors via Route 11
Route 1A, Cross Roads to Mount Mellick
Route 2, Tignish to Souris
Route 3, Cherry Valley to Georgetown
Route 4, Wood Islands to Dingwells Mills
Route 5, Mount Albion to Cardigan; used to extend to Dingwells Mills via Route 4
Route 6, Kensington to Bedford
Route 7, Milton to Oyster Bed Bridge
Route 8, Ross Corner to New London
Route 9, Long Creek to Brookfield
Route 10, Central Bedeque to Tryon
Route 11, Inverness to Reads Corner and St. Eleanors
Route 12, North Cape to Miscouche
Route 13, Crapaud to Cavendish
Route 14, North Cape to Carleton
Route 15, Charlottetown to Brackley Beach
Route 16, St. Peters to Souris
Route 16A, Lakeville to South Lake
Route 17, Murray River to Montague
Route 17A, Cambridge to Sturgeon
Route 18, High Bank to Murray River
Route 18A, White Sands to Murray Harbour
Route 19, DeSable to Cornwall
Route 19A, Canoe Cove to New Dominion
Route 20, Kensington to New London
Route 21, Southport to St. Patrick Road
Route 22, Mount Stewart to Victoria Cross
Route 23, Orwell to Wood Islands
Route 24, Vernon River to Murray River
Route 25, Marshfield to Stanhope
Route 25A, Covehead Road to West Covehead

Three-digit routes that look notable are:

Route 107, Reads Corner to Clinton: collector southwest of Norboro
Route 121, Summerside to Sherbrooke: thick line on the official map
Route 122, St. Nicholas to Southwest Lot 16: collector
Route 124, Abram-Village to Wellington: thick line on the official map; collector
Route 131, Wellington to Birch Hill: collector north of MacDougall
Route 133, Mount Pleasant to Ellerslie: thick line on the official map
Route 142, West Cape to Roxbury: thick line on the official map; very thick (arterial) beyond O'Leary (to Woodstock)
Route 150, Campbellton to Alberton: arterial and collector east of Elmsdale
Route 152, Ebbsfleet to Northport: thick line on the official map; partly collector
Route 153, Montrose to Christopher Cross: thick line on the official map (to Tignish); collector
Route 167, MacDougall to Tyne Valley: collector
Route 178, Northam to Tyne Valley: thick line on the official map, along with a bit of Route 132 from Route 2
Route 225, Middleton to Warren Grove: thick line on the official map, along with a bit of Route 248 to North River; both collectors
Route 258, New Glasgow to Rusticoville: thick line on the official map; collector
Route 313, Cardigan to Greenwich: thick line on the official map; collector south of Cardross
Route 315, Wood Islands to Montague: thick line on the official map; collector
Route 321, Roseneath to Morell: collector north of Cardross

Arterials and collectors are listed at [1].

Other notable roads are:

Charlottetown Perimeter Highway, as well as Upton Drive and Riverside Drive connecting each end to Route 1: arterial

The following one- and two-digit routes are local (not arterials or collectors):

Route 1A (east segment)
Route 5
Route 8 north of Summerfield
Route 9
Route 10
Route 11 west of Miscouche (partly unpaved)
Route 12: north of Alberton, Portage to Ellerslie, Tyne Valley to MacDougal, Southwest Lot 16 to Miscouche
Route 14 (partly unpaved?)
Route 16 north/west of South Lake
Route 17
Route 17A
Route 18A
Route 19: south/west of New Dominion
Route 19A
Route 20: east of Malpeque
Route 21: east of Pisquid (partly unpaved)
Route 22: south of New Perth
Route 25A

There are also a few scenic heritage roads.