Ontario has started construction to widen 18 kilometres of Highway 401 from Mississauga to Milton.

The Ford government says the $640 million project will reduce congestion, shorten commute times and encourage economic growth in the region.

"This crucial expansion of Highway 401 means that thousands of Ontarians will spend less time in traffic and more time on the things that matter to them — being with family, friends or at work," said Associate Minister of Transportation Kinga Surma in a news release.

Work has started and is scheduled to be completed by 2022.

The redesigned highway will feature:

A 12-lane core-collector system from Credit River to Winston Churchill Boulevard.

10 lanes from the Winston Churchill Boulevard to the Highway 407 ETR/Highway 401 interchange.

A 12 lane core-collector system from Highway 407 ETR/ Highway 401 interchange to James Snow Parkway.

10 lanes from James Snow Parkway to RR 25.

Median High Occupancy Vehicle (HOV) lanes.

New or improved support facilities and features, such as drainage, lighting, signage and carpool lots.

However, some transportation planners say expanding highways does not reliably lead to reduced traffic or congestion due to a phenomenon known as induced demand.

That idea suggests that widening highways encourages more people to drive cars, negating the benefits of adding capacity.

The highway expansion project comes after the Progressive Conservative government raised speed limits to 110 kilometres per hour on three sections 400-series highways.

According to the province, approximately 250,000 vehicles travel on Highway 401 in the Peel and Halton regions every day.