of the Canton de l'Est extension of Quebec's Autoroute 10 eastwards from Montreal. One possible routing for an "east-west freeway" would travel due west from Interstate 95 near Waterville, following the U.S. Route 2 corridor through Maine, New Hampshire, Vermont, and upper New York state. The more northerly-located link to Québec would exist with Autoroute 73, whose Chaudière-Appalaches proposed southeast extension within Quebec could link through, and generally heads directly towards (as Quebec Route 173 already does) the existing Armstrong–Jackman Border Crossing some northeast of Coburn Gore, despite no link to the American Interstate Highway System existing or planned to exist to it. Only the two-lane U.S. Route 201 - Maine State Route 6 currently has a northern terminus at that specific port of entry. There are two existing mainline freeway links on both sides of the border between New England and Canada: the north-south linkup at the Derby Line–Rock Island Border Crossing, between Interstate 91 in Vermont and Quebec Autoroute 55 (opened in 1978), and the crossing between Interstate 95 and New Brunswick Route 95 at the Houlton–Woodstock Border Crossing. An additional crossing is anticipated further west between Vermont and Québec, with an expected linkup between Interstate 89, which already ends at the international border at the Highgate Springs–St. Armand/Philipsburg Border Crossing, and Quebec Autoroute 35, via the Autoroute's planned extension from its current southern terminus at Saint-Sébastien to the international border. There are plans to complete the extension of Autoroute 35 from Saint-Sébastien to the border crossing at I-89's northern terminus by 2023, finally creating a freeway-to-freeway connection. Northern New England is served by three north–south freeways radiating generally northwards from Boston — from east to west, Interstate 95, Interstate 93, and U.S. Route 3, all coming from or through the Boston metro area; and westernmost of all, by Interstate 91, which follows the Connecticut River. However, the northernmost complete east–west freeway existing within the region, Interstate 90 in Massachusetts, does not enter northern New England. Continuous east–west freeway travel through (and within) northern New England is presently accomplished by three segments, only one of which is truly east-west: Interstate 89 is generally a northwest/southeast-running highway over the portion of its route from Burlington, Vermont, to its southern terminus at Interstate 93 near Concord, New Hampshire. I-93 continues the southeast direction of travel to Manchester, New Hampshire. New Hampshire Route 101 is freeway standard from I-93 in Manchester