GoCarma activates automatically when you travel in a TEXpress Lane and uses a combination of GPS and Bluetooth to verify your HOV status. This only happens during weekday peak periods.
However, if you prefer not to have your occupancy confirmed in a vehicle for the purposes of qualifying for HOV toll discounts, it's easy to opt out.
You can opt out at any time by doing any one of the following:
Log out of the GoCarma app
Disable location services on your phone
Deleting the GoCarma app from your phone