English: A new "switchable" FasTrak transponder device developed for the Metro ExpressLanes project. Unlike most High occupancy/toll and express toll lanes in the world, the toll lanes in the Metro ExpressLanes system require all drivers, HOV and solo, to carry a transponder. So that HOVs aren't charged a toll, the driver sets the switch on the FasTrak to indicate how many occupants (including the driver) are in the vehicle. This also allows for different HOV limits depending on time; e.g., on the I-10 freeway, during peak hours HOV is considered three or more occupants in the vehicle, while at other times it is two or more. Most other HOT lane systems don't require HOVs to carry transponders, and ask those that do to put their transponder in a mylar bag so it isn't read. There are a few reasons why Metro requires HOVs to carry a transponder, but mostly to allow them the ability to monitor congestion in more detail, tracking solo drivers as well as HOVs.