Carpooling, a way to decarbonize road mobility in smart cities & metropolitan areas

As they were already used in the 1960s on the roads, carpooling-lanes are now part of an ensemble of layouts to run and optimize the road network. They also have an environmental impact thanks to the decrease of pollution that represents shared mobility. These lanes are mainly made for workers and other commuters who travel mostly mornings and late afternoons, in large number. In France, the idea is to reserve the far left lane to the carpoolers on roads which have three lanes or more. It is a key leverage in case of large traffic jams on these lanes but also for the air quality. However, is it possible to make our current roads coexist with carpooling lanes?