How does FasTrak Know if you are a Carpool
By doing this, the driver sends a signal to the electronic gantries that there are other occupants in the car. However, as this can be misused by someone driving alone, there are California Highway Patrol (CHP) Officers dedicated to express lane rule enforcement. They get notified for every vehicle that signals being carpool and randomly check a vehicle to verify it. In case of misuse, a fine is issued to the driver.
Note: FasTrak Flex is not the same as a regular FasTrak toll tag. It offers discounts for carpools on I-580, I-880, I-680 Contra Costa and SR-237 express lanes in California.