High-Occupancy Vehicle (HOV) lanes are dedicated expressway lanes for vehicular traffic that comply with the regulatory signage for that specific lane. These lanes can be used by vehicles that are carrying two or more people.

HOV lanes are located in some areas of the 400-series highway. These areas are clearly marked with signage indicating the entry and exit points for the lane. These are designated points and marked with broken white lines and pavement markings. Drivers are not permitted to enter or exit a HOV lane by crossing a striped buffer zone. It is illegal. Only emergency vehicles with light and sirens activated are allowed to cross the striped buffer zones.

On the 400 highway between Major Mackenzie Drive and King Road, there is a different type of HOV lane. This HOV lane includes a dedicated transfer lane for movement between the regular (passing) lane and the HOV lane. This lane is used to merge in or out of the HOV lane.

If a driver is spotted by OPP for using the HOV lane incorrectly, they could face a fine of $110 and 3-demerit points.