What it means
The HOV (High-Occupancy Vehicle) Diamond Lane sign marks a lane reserved for vehicles carrying the minimum number of occupants specified on accompanying signs — typically two or more persons (HOV 2+) or three or more (HOV 3+). The lane is marked with white diamond symbols painted on the pavement and is separated from general-purpose lanes by a solid double-yellow line or a buffer zone.
Where you'll see it
On freeways and expressways in high-traffic metropolitan areas. California has one of the largest HOV lane networks in the US, covering major corridors in the Los Angeles, San Francisco Bay Area, San Diego, and Sacramento regions. HOV lanes are also common in Seattle, Denver, Atlanta, and Washington DC metro areas.
What to do
Only enter an HOV lane if your vehicle meets the occupancy requirement during the posted hours. Check signage carefully — some HOV lanes operate only during peak commute hours (e.g., 6–9 AM and 3–7 PM on weekdays), while others are 24/7. Clean-air vehicles with a California DMV HOV decal may use the lane regardless of occupancy in states that permit it, though decal programs have eligibility deadlines.
Common mistakes
Crossing a solid double-yellow line to enter or exit an HOV lane is illegal and carries its own fine on top of any HOV violation penalty. Enter and exit only at the designated breaks in the lane markings.