It was originally envisioned that Autoroute 20 would extend from the
Turcot Interchange, along the route of the 720, to the
Louis Hippolyte Lafontaine Bridge-Tunnel. Indeed, when the first section of the expressway was constructed and opened in the early 1970s, many Montrealers, anticipating that it would eventually replace the
Metropolitan Expressway as the primary connector route to the Lafontaine Tunnel, and onward to
Quebec City, dubbed the then-unnamed roadway the "Downtown
Trans-Canada Highway". The
provincial transport ministry (Le ministère des Transports du Québec, or MTQ) had planned to extend the Viger Tunnel east to
Autoroute 25 at its Souligny Avenue interchange. The right-of-way has existed since the original layout of the A-720, and buildings along the extension were demolished at that time, even though the 720 was not completed due to cost constraints. The government of Montreal instead converted the portion of Rue Notre Dame east of the Jacques Cartier Bridge into a six-lane
urban boulevard, rather than continue a sunken limited-access expressway. The final project was approved, and work began on Souligny Avenue to double the span of the travel lanes. In 2007, working crews for
Transports Québec discovered major cracks in a support pillar and closed several lanes of the expressway. Transports Quebec announced on August 10, 2007, major repair projects for a large section of the Expressway west of the Ville-Marie tunnel. On July 31, 2011, part of the roof of the Ville-Marie Tunnel collapsed, sending large chunks of concrete to the road below. This incident occurred at a time with little traffic and no vehicles were damaged. Several construction workers were on site at the time and were unharmed. The tunnel had to be closed for repair of the roof and several other parts of the tunnel. Transport Minister Sam Hamad announced on Friday, August 5 that the tunnel would re-open the following day. In 2021, the A-720 was renamed to Route 136 due to the highway having reduced lane sizes following the reconstruction of the
Turcot Interchange. ==Exit list==