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The system monitors the freeway and raises or lowers the toll to keep traffic flowing smoothly in the express lanes. San Mateo 101 Express Lanes use “dynamic pricing” to set the toll price. Dynamic pricing is when the price to use the lane goes up or down depending on how crowded the lane is. Overhead message signs tell drivers the price to travel to a destination in the toll lane. Tolls will be paid using FasTrak®.

All vehicles need FasTrak® or FasTrak Flex® to use the lanes.

  • 3+ person carpools, vanpools, buses, and motorcycles can use the lane for free
  • 2-person carpools can choose to pay 50% of tolls with FasTrak Flex®
  • Solo Clean Air Vehicle (CAV) drivers can choose to pay 50% of tolls with CAV FasTrak Flex®
  • Solo drivers can choose to pay full tolls with FasTrak® or FasTrak Flex®


Before starting your trip, solo drivers must set their FasTrak Flex® toll transponder to the “1” position so the toll system can charge the vehicle the proper toll. Carpools with two occupants would set the toll transponder to the “2” position to get a toll discount. Carpools with three or more occupants or motorcyclists must set their toll transponder to the “3+” position. The “2” and “3+” settings allow eligible vehicles to use the lanes toll-free or for discounted tolls. These toll transponder settings also trigger beacons that  CHP officers use to enforce vehicle occupancy requirements.

Cars with a valid Clean Air Vehicle decal wishing to get a discount will need to use a CAV FasTrak Flex® toll tag. To register for the Clean-Air Vehicle Fastrak Toll Tag, visit FasTrak.

No. Drivers only need one toll transponder in the vehicle. Standard FasTrak transponders should be returned and be replaced with a FasTrak Flex® transponder. If multiple transponders are in a vehicle, the toll system may detect the additional transponder(s) and the trip may result in multiple toll charges. FasTrak Flex® can also be used to pay for Bay Area bridge tolls.

You can enter or exit the US 101 Express Lanes in San Mateo County at any point.

Two-person carpools in two-seater vehicles can travel toll-free in the US 101 Express Lanes in San Mateo County. Please set your FasTrak Flex transponder in the “3+” position before driving.

US 101 Express Lanes in San Mateo County operate Monday – Friday 5am-8pm. Outside of these hours, the lanes are open to all drivers at no charge.

Click here for assistance with toll violations.