MONTREAL -- Cars carrying two or more people should be able to drive in bus lanes, the municipal opposition contended on Monday, declaring that such a move would reduce traffic.

By glancing at traffic, any observer can tell that most vehicles in Montreal have only one occupant.

"This is a very simple solution, one that can be implemented in a short time frame with very little cost. And it will have real concrete impacts," said Lionel Perez, the leader of the municipal opposition. "A reduction of greenhouse gases and reduction of time."

Perez and his party, Ensemble Montreal, presented a motion on Monday, proposing that vehicles with two or more people be allowed to use bus and taxi lanes.

Bus lanes cover close to 100 kilometres of Montreal's streets. Allowing carpool vehicles onto those lanes would significantly reduce traffic, Perez said.

But the proposition would make it difficult to know who's following the rules, according to Rick Leckner, a traffic expert. "There are cheaters now," he said. "If you're going to open up bus lanes to cars, it's going to be difficult to make sure that cars with two or three people are in them."

Municipal politicians will debate the motion at city hall on March 23.