Your green licence plate is a sign of your commitment to a cleaner Ontario. Until June 30, 2016, electric vehicles with green plates will be granted access to HOV lanes on 400-series highways and the QEW, even if there is only one person in the car. HOV lanes are otherwise reserved for vehicles carrying two or more people.
For more details visit http://www.mto.gov.on.ca/english/vehicles/electric/green-licence-plate.shtml.