The state’s free Flex Pass incentive for carpoolers and free motorcycle pass for regular I-405 drivers continues through the end of March.

Over 33,000 of the free Flex Pass transponders have been given out since last spring.

Having a Flex Pass turned to HOV mode and linked to an active Good to Go account is the only way to travel toll-free in the I-405 express lanes as a carpool.

Less than one-third of the free passes went to regular carpools. Of those getting a pass, 29 percent said they carpool four or more times per week; 39 percent said they team up two or three times a week; 32 percent said once a week.

To qualify for a free pass, drivers need to “live, work or play” in King and Snohomish counties, and carpool at least once a week on I-405 — including weekends.

The incentive program is offered through RideshareOnline.com, which helps area drivers find carpool partners.

Lynnwood, Everett and Snohomish made the top 10 cities for drivers requesting free Flex Passes.

Carpool rules now require three or more occupants during peak morning and afternoon workday commutes for the toll-free incentive.

Most of those who drive the express toll lanes are paying drivers — as many as 85 percent.

During the morning rush the week of Nov. 30, for example, 15 percent of 61,500 trips in the express toll lanes had a pass switched to HOV mode. Northbound in the evening, it was 16 percent of 73,000 trips.

Over the full day, drivers who declared HOV status with a Flex Pass made up about 1 in 4 of all users during weekdays in November. That includes 3-plus carpoolers during peak hours, and 2-plus all other times of day.

That marked a 29 percent increase from October, when HOV users represented about one-fifth of all trips. In contrast, the number of paying trips per day decreased by less than 5 percent that month as toll rates increased.

Weekends also saw a rise in carpool usage. In October, one-fifth of trips were in HOV mode. In November, nearly half of all weekend trips were HOVs. Weekend carpool requirements remain at two or more occupants but still require a Flex Pass and Good to Go account.

The figures don’t capture those who have kept two-person carpools during rush hours, such as those who buddy up in order to split toll costs.

The state plans to do a visual count of how many bodies are in vehicles in the spring — when there is more daylight — following guidelines set out by the University of Washington for such surveys.

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