How do carpool lanes in the US work?

  • I'm doing some research for our roadtrip through SW USA (+Calif.) and ran into "carpool lanes" and this came to my attention:

    Hopefully if you're not travelling alone, you will be allowed to drive through carpool lanes that help go past single-occupancy traffic

    Since we're travelling with 2 (and part of the trip with 4), is it safe to say I can always use the carpool lanes? If more than 2 (e.g. 3) persons are required, is there a clear traffic sign that states this or do I have to know the rules in each state/city by heart?

    I also found that 2 freeways in LA County (I-10 and I-110) were converted to toll roads and require RFID transponders. I suppose a rented car doesn't have a transponder? Is it made clear by any sign that you need a transponder?

    the rules for carpool lanes are usually written on signs. And they usually apply for rush hours.

    @Vince: In my experience, in Southern California, the carpool lane rules generally apply at all times. However, in Northern California they tend to be marked as only applying M-F 6-9AM 3-7PM or similar, i.e. rush hour. They are marked on signs but are not always easy to figure out on the fly if you are not familiar with the system.

    Around here the lanes are marked HOV (High Occupancy Vehicle) with hours but no number. The law says 2 but there's no way to know that while just driving down the road.

    Definitely check the hours on the signs. I have encountered such lanes that switch directions based on the time of day.

    Note - "in the US" is not very helpful/useful here; this is state-based (and in some cases even smaller, city/county-based) and different states will have entirely different rules.

    Interstate 80 to and from the SF Bay Bridge has a 3-person carpool lane; other Bay Area freeways are 2. It's signed. As for rental cars, they will rent you a transponder for a fee, which will be added onto the tolls you accumulate. I assume the fee is because they have to wait until they receive their own bill to collect from you.

  • DavGin

    DavGin Correct answer

    8 years ago

    At the entrance of a carpool lane, a sign always indicates how many people are required in each vehicle to be eligible, since situations sometimes vary.


    In Los Angeles area, nearly all carpool lanes have a minimum of 2 passengers.

    I only have seen one case in which three passengers were required. At the time of my visit in 2009, the freeway heading east of Union Station to El Monte had passenger requirements that depended on the time and day of week. In normal hours, 2 passengers were enough; in weekday posted rush hour times, the requirement was 3 passengers.

    Be careful in the area : now, there is a new system called ExpressLanes running on I-10 and I-110 freeways. The concept is that people not eligible to enter the lane may buy their way in by paying a congestion-priced toll, instead of getting a fine. Toll collection happens electronically, and uses a compulsory transponder. Legitimate carpoolers who used to simply drive through the lane are now required to have the transponder on ExpressLanes, even if no toll is charged for them. The transponder has a switch to indicate the number of occupants.

    Other freeways still have the "classic" carpool lanes.

    Found this link for Canada, I suppose it's similar looking for the US ?

    When it says "2 passengers", does it include the driver? I.e. if there is only the driver and one other person in the car, do they count as "2 passengers"?

    @Grzenio: The usual wording is actually "2 or more *persons* per vehicle" (example), which makes it unambiguous that the driver is included.

    Yes, I fixed it, it's actually "persons" including the driver.

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Content dated before 7/24/2021 11:53 AM