THE FASTRAK FLEX TOLL TAG
The FasTrak Flex toll tag works like a standard FasTrak toll tag and has an additional feature required for carpools in the I-580 and I-680 Contra Costa express lanes.
The FasTrak Flex toll tag works as a standard FasTrak toll tag but also has a three-position switch to signal whether you are travelling as a carpool or alone. It is the carpool toll tag for all Bay Area Express Lanes.
The standard FasTrak toll tag works at all Bay Area toll bridges, in express lanes for solo drivers, and pays SFO parking.
Should You Get a FasTrak Flex Toll Tag?
Yes, for carpool travel in the I-580 and I-680 Contra Costa express lanes.
Get the FasTrak Flex toll tag if you want to travel toll-free as a carpool, motorcycle, or eligible Clean Air Vehicle (CAV) in the new I-580 and I-680 Contra Costa express lanes. The FasTrak Flex toll tag also works as a standard FasTrak toll tag. It pays bridge tolls, express lanes as a solo driver, and parking at garages displaying the FasTrak logo.
Yes, if you want more convenient travel as a carpool in other express lanes.
The FasTrak Flex toll tag is a convenience, but is not required, for toll-free travel in the SR-237 and I-680 Sunol express lanes as a carpool, motorcycle, or eligible CAV. If you have a standard FasTrak toll tag, you must enclose it in a Mylar bag to avoid being charged a toll. If you have a FasTrak Flex toll tag, you can leave it mounted on your windshield and use the switch position to identify your vehicle for toll-free travel.
Otherwise, no.
The standard FasTrak toll tag will serve all your needs if you do not use express lanes as a carpool. There is no need to obtain a FasTrak Flex toll tag. The vast majority of FasTrak users do not need a FasTrak Flex toll tag.

Note: To receive carpool discounts at toll bridges, you must use a designated carpool lane.
How to Use the FasTrak Flex Toll Tag
Before your trip, set the switch position on your FasTrak Flex toll tag as shown below. Position (2) and (3+) signals that you are a carpool, motorcycle, or eligible CAV and qualify for toll-free travel.

You can carpool toll-free in the midday, too
It takes only two people to be a carpool and travel toll-free, any time between 5 am to 8 pm, Monday through Friday including holidays in the I-580 and I-680 Contra Costa express lanes. A FasTrak Flex toll tag is required, so get yours today.
TIP
How to Exchange Your Standard FasTrak Toll Tag for a FasTrak Flex Toll Tag
Online
Log into your FasTrak account. Click on Vehicles & Tags, then Order A Toll Tag. Enter the number of FasTrak Flex toll tags you wish to receive and then click Continue and Submit your order.

You can return your standard toll tag to the Customer Service Center in person or by mail. If you are mailing a toll tag, we recommend that you use certified or registered mail to ensure delivery. However, if you wish, you also can put the toll tag into the mail without an envelope or postage. The mailing address is already written on the toll tag and the post office will deliver the toll tag to us.
By phone
Call our Customer Service Center and tell them you want a FasTrak Flex toll tag as a replacement for your standard toll tag. Also, provide the toll tag number of the standard toll tag you will be returning, so that FasTrak can deactivate it. We will mail a FasTrak Flex toll tag and a return envelope with pre-paid postage to you. Please put your standard toll tag into the envelope and mail it back to us.

To get started, call us at 1-877-BAY-TOLL (1-877-229-8655).
Toll tag security deposit
The toll tag you order may require a security deposit. When the Customer Service Center receives a toll tag back from you, we will adjust your security deposit accordingly.
Express Lanes
Using Carpool Lanes
Bay Area Express Lanes
I-580 Carpools
I-680 Contra Costa Carpools