Quebec Autoroute 20

The A-20 begins at the Ontario-Quebec border near Rivière-Beaudette as the continuation of Ontario Highway 401. The westernmost section of the A-20 was named the Autoroute du Souvenir (Remembrance Highway) in 2007 to honour Canadian veterans. Road marker signs on this stretch of the autoroute feature a poppy (a traditional symbol of Remembrance in Canada).

At km 29, the A-20 crosses A-30 (former A-540) before becoming an urban boulevard for approximately eight kilometres (km 30 to 38) in Vaudreuil-Dorion and L'Île-Perrot. This stretch of highway takes the A-20 across the Ottawa River. The speed limit is 50 km/h (30 mph) in Vaudreuil-Dorion and 70 km/h (45 mph) in L'Île-Perrot. The A-20 once again becomes a limited-access highway at km 38, just before crossing the Sainte-Anne-de-Bellevue Canal onto the Island of Montreal.

The A-20 then traverses the West Island (in French, l'Ouest de l'Île) along the north shore of Lac Saint-Louis to an interchange with the A-520. Commonly called the Dorval Interchange, this exit is the main access to Montreal's Trudeau International Airport. Further east, the A-20 crosses the A-13 at its southern terminus, and then, at the St. Pierre Interchange, Route 138 west towards the Mercier Bridge.

Just west of downtown Montreal, the A-20, A-15, and A-720 meet at the Turcot Interchange. In 2020, the completion of a major project involving the rebuilding of the Turcot Interchange has shifted the autoroute north between Route 138 and the Turcot Interchange. From this interchange, A-15 continues north to Laval while A-20 east is multiplexed with A-15 south on the approach to the Samuel-de-Champlain Bridge. Traffic bound for the city centre continues as the A-720 (Autoroute Ville-Marie).

Multiplexed with the A-10 and A-15, all three autoroutes cross the Saint Lawrence River via the Samuel-de-Champlain Bridge to the South Shore (in French, Rive Sud). The multiplex splits south of the bridge. The A-20 parallels the south shore of the river through suburban Longueuil. The junction with the A-25 affords a direct connection to the Louis Hippolyte Lafontaine Bridge-Tunnel and Montreal's East End. The Trans-Canada Highway joins the A-20 at this junction.

Autoroute 20 in Saint-Michel-de-Bellechasse with the Saint Lawrence River and the Laurentian Mountains at the background

The largest section of the A-20 (from its junction with A-25 to its easternmost terminus) is named after Jean Lesage, who served as Premier of Quebec from 1960 to 1966, during the Quiet Revolution. Autoroute Jean-Lesage currently exists as two discontinuous sections separated by about 55 kilometres:

• The main section between the Louis-Hippolyte-Lafontaine Bridge-Tunnel and Trois-Pistoles in the Bas-Saint-Laurent region.
• A shorter section that serves as a bypass of Rimouski and extends east to a final terminus at Route 132 in Mont-Joli.

From the junction with A-25, the A-20 travels east, away from the St. Lawrence River. At kilometre 98, the A-20 intersects the A-30 near Mont Saint-Bruno, crossing the Richelieu River (km 112) just north of Mont-Saint-Hilaire. Bypassing Saint-Hyacinthe, the A-20 forms a multiplex with Route 116 for six kilometres between exits 141 and 147. This section of the A-20 in Centre-du-Québec is located the furthest from the St. Lawrence River (approximately 45 kilometres). Between Drummondville and Sainte-Eulalie, the A-20 forms a multiplex with A-55 for 37 kilometres.

The A-20 continues across the St. Lawrence Lowlands and Quebec's agricultural heartland. The autoroute once again parallels the river as it approaches metropolitan Quebec City. From this point eastward, the A-20 is never more than five kilometres from the river. At km 312, the A-20 crosses the A-73, a north–south link between Saint-Georges and Quebec City via the Pierre Laporte Bridge. While the control city on the A-20 is listed as "Québec", the autoroute never enters the city proper. Before departing the region the A-20 bypasses suburban Lévis.

Autoroute 20 westbound in Montreal, ~km 66

This section of the A-20 offers the motorist splendid views over the St. Lawrence River and the mountains of the Côte-Nord, especially Mont-Sainte-Anne and Le Massif. As it continues eastward, the A-20 passes the regional centres of Montmagny and La Pocatière before approaching Rivière-du-Loup and the junction with A-85 at km 499. The Trans-Canada Highway departs the A-20 at this interchange and travels southeast on A-85 toward Edmundston, New Brunswick and the Maritime Provinces. The eastern end of the main section of the A-20 is located in Trois-Pistoles, approximately 40 kilometres east of Rivière-du-Loup.

The second section of Autoroute Jean-Lesage (km 597 to km 641) connects Rimouski to Mont-Joli. It begins at a junction with Route 132 in the village of Le Bic, approximately 55 km from the current terminus of the A-20 main section. Like its larger counterpart, the Rimouski section of the A-20 parallels the St. Lawrence, providing a southern bypass of Rimouski before ending (at another junction with Route 132) at the western approach to Mont-Joli.

This section of the A-20 is currently a single carriageway with occasional passing lanes. It was built to accommodate an eventual expansion to four lanes and most overpasses include the clearance needed to accommodate the additional lanes. The high accident rate along this section of the A-20 have prompted many politicians to call for the highway to be expanded to two lanes in each direction.

An electric fence has been installed on both sides of the highway between km 621 and 628 to prevent moose from crossing the road, while at km 624 an underpass has been constructed to allow wildlife to pass under the highway safely.

The MTQ plans to rebuild A-20 (currently an urban boulevard) through Vaudreuil-Dorion and Île-Perrot as a limited-access highway. There is no timeline for this project presently.

Long-range plans by the MTQ call for the two sections of the A-20 to meet. A 9.8 km section of single carriageway was opened to traffic on December 3, 2011 between Cacouna and L'Isle-Verte. As part of this project, a few kilometres of the highway near Cacouna was moved 1.5 km to the south and the old roadbed was destroyed. The MTQ timeline for completing the highway to Trois-Pistoles was met; it opened to traffic in November 2015. Overpasses were constructed for the St-Paul, St-Éloi and Drapeau roads.

Regarding the section from Trois-Pistoles to Le Bic, the Quebec government has completed environmental and economic reviews of the impact of linking the two sections of Autoroute 20,[3] but it has not committed the funds necessary for construction. Frustrated by the long delay in linking the two sections of the A-20, in 2013, the Mayor of Rimouski proposed paying for the construction by tolling the autoroute.[5]

Citing predictions for an increase in ferry traffic to and from the Côte-Nord as a result of the Government of Quebec's Plan Nord, in 2011 the Mayor of Matane called for the further extension of the A-20 to his city.[6]