High-occupancy lanes, high-occupancy toll lanes and express toll lanes can be confusing. Here's a rundown on some of the rules of the road.

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Sterling Cassel knows he’s the source of some driver’s fury on Interstate 405.

“Sometimes I’ll be in the left lane to exit at either Sixth Street in Bellevue or 128th Street in Kirkland, and people will get frustrated and zoom around me,” said Cassel, who drives in a carpool between Bothell and Bellevue.

He wrote in to Traffic Lab in search of the proper etiquette for traveling in express toll lanes where there are two lanes.

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, CenturyLink, Kemper Development Co., PEMCO Mutual Insurance Company, Sabey Corp., Seattle Children’s hospital and Ste. Michelle Wine Estates. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

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“Is it treated like a highway, where the right lane is the travel lane and the left lane is the passing lane, like in a normal freeway or highway situation, or is it just sort of free-for-all?” Cassel asked.

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In particular, he said, when traveling at the posted 60-mph speed limit, “it seems like people pass you like you’re standing still.”

So what gives?

The Washington State Department of Transportation (WSDOT) points to Title 46, Section 100 in state law dealing with roadway passing.

It generally says that drivers should stay in the right lane, except when passing another vehicle, traveling at a faster speed than traffic flow, or allowing other cars in to merge.

“So if a driver moves to the left to allow for traffic merging into or out of the Express Toll lanes, the driver should then move right if they are impeding traffic,” Frances Fedoriska, of WSDOT communications, wrote in an email to Traffic Lab.

There are three different types of special-capacity lanes along state highways and interstates:

  1. High-occupancy vehicle lanes: These are portions of the roadway reserved for cars carrying typically two or more passengers, including transit vehicles.
  2. High-occupancy toll lanes: These require two or more people in the car to travel toll-free and for solo-drivers to pay a toll. An example of such lanes is on Highway 167, where a Good To Go! Flex Pass is optional for carpoolers and motorcycles.
  3. Express toll lanes: These are similar to high-occupancy toll lanes. An example is on I-405, where a Good To Go! Flex Pass is required for carpools and motorcycles. Drivers are required to pay a toll if riding solo, and the number of occupants needed to avoid a toll depends on the time of day.

Because express toll lanes are restricted lanes, said Rick Johnson, a Washington State Patrol public information officer, they do not fall under the law that penalizes “left-lane campers.”

However, he said, “It is best practice to use the left toll lane just to pass.”

Otherwise, Johnson said, it “might lead to aggressive driving or road rage when a driver believes the other vehicle should move out of their way because they want to go faster.”

High-occupancy lanes are designed to encourage carpooling, prioritizing the movement of large numbers of people over solo-driven cars.

However, non-HOV drivers may take advantage of the Interstate 405 express toll lanes and Highway 167 high-occupancy toll lanes if they are willing to pay a toll. Motorcyclists are allowed to use all standard HOV lanes.

Rates can range between 50 cents and $9 for Highway 167, and between 75 cents and $10 for I-405. They adjust depending on traffic conditions and demand.

To avoid toll payment along I-405 between Northeast Sixth Street in Bellevue and Interstate 5 in Lynnwood, drivers need to have the required number of occupants.

  • Two or more people are needed within a single vehicle between 9 a.m. and 3 p.m.
  • Three or more people are required in a vehicle between 5 and 9 a.m. as well as between 3 and 7 p.m.

The I-405 express toll lanes are open to most vehicles on weekends, certain holidays and overnight after 7 p.m. and before 5 a.m.

Do you carpool to work? We’d like to know how it’s going

Traffic Lab is interested in your experiences forming carpools. How did you go about finding fellow riders? How much time or money did you save — or spend? Or maybe you tried it, but it didn’t work out. Contact reporter Michelle Baruchman at mbaruchman@seattletimes.com or 206-652-6588 to share your experiences.

We may publish your story as part of Traffic Lab’s coverage of commuting.