Motorists who like to drive in a more compact fashion — sports cars, small pickups and Smart cars — are about to get the squeeze.

Starting Jan. 1, high-occupancy vehicle express lanes on Interstate 25 and the Boulder Turnpike will be free for cars with three or more occupants only, forcing owners of two-seater vehicles to pay up if they still want to travel in the carpool lane.

For Don Gordon, former vice president of the Z Car Club of Colorado, bumping up the minimum number of passengers in a car from two to three to qualify for free use of carpool lanes — a concept known as HOV 3 — without carving out an exemption for vehicles that aren’t built to hold more than two people is frustrating.

“I feel like I’m being discriminated against,” the Aurora resident said.

It’s especially vexing due to the fact that motorcycles will continue to be allowed to use the HOV express lanes without having to cough up a penny for the privilege, Gordon said.

“I would think there are more people driving two-seaters than are riding motorcycles,” said Gordon, who likes to take his Nissan 350Z out for a spin from time to time. “This is silly — somebody must not have thought this through.”

But the Colorado Department of Transportation said the state’s new HOV 3 policy was thoroughly vetted before being put into place. Amy Ford, an agency spokeswoman, said tolled HOV 3 lanes were adopted by the CDOT’s Transportation Commission nearly four years ago — to start operation in 2017 — primarily as a way of ensuring reliable travel speeds on Colorado’s increasingly crowded and underfunded highways.

CDOT teamed up with private consortium Plenary Roads Denver to build, operate and collect tolls on the managed lanes in the metro area. Without that public-private partnership, CDOT wouldn’t have had the money to add capacity to U.S. 36 and I-25 for years, Ford said. The trade-off was moving from the two-occupant HOV system now in place to an HOV 3 system encompassing all vehicles except motorcycles, which are protected by federal law from having to pay to use carpool lanes.

“A lot of the financial modeling (for the expansion projects) was predicated on going with HOV 3,” she said.

Ford acknowledged that owners of dual-seat vehicles, including Miatas, Smart cars, small-cab pickups and Corvettes, will be “impacted” by the new policy but noted they still ultimately retain the choice of how to travel.

“The carpool eligibility is a particular use of the lane, but it doesn’t preclude you from being able to use it — it just precludes you from being able to use it for free,” she said. “HOV is not about filling a vehicle, it’s about moving people in an HOV capacity.”

Colorado is not the only state to tell two-seat vehicle owners to go pound sand. Virginia also makes such cozy car drivers pay to use its HOV 3 lanes.

“We have to increase throughput of people, not vehicles,” said Tamara Rollison, a spokeswoman for the Virginia Department of Transportation. “Now when we make transportation improvements in northern Virginia, it’s about moving more people with fewer vehicles. We simply don’t have enough pavement for single vehicles.”

But on the other side of the country, California does make an exception for two-seat cars, though only in the Bay Area. According to the Caltrans website, “originally factory designed vehicles with a maximum two-seat occupancy may access the HOV(3+) lanes as long as there are two occupants in the vehicles.”

The California legislature in 1995 granted an exception to two-seater vehicles to cross the Bay Area’s toll bridges in the HOV 3 lane at a reduced charge or toll-free and, for simplicity’s sake, extended that privilege to the rest of the toll road system in and around San Francisco, according to Caltrans spokeswoman Angela DaPrato. Since the only toll bridges in California are in the Bay Area, DaPrato said that is the only place in the state where the exemption is made.

That’s the way Brian Baumbach, a Douglas County resident and a member of the Peak to Peak Miata Club, thinks it should be in Colorado.

He was driving his 2001 crystal-blue Mazda Miata with his wife on I-25 recently when he saw the overhead signs warning of the switch to HOV 3 on the first of the year. His first thought was that by including two-seat vehicles into the paying class of vehicles in the HOV lane, Plenary Roads was simply looking for new ways to “increase their profits.”

“It seems a bit unfair,” he said. “If your vehicle is full, it should be allowed to travel in the HOV lane for free.”

Some state lawmakers have sympathy for the conundrum faced by Colorado’s class of dual-seat drivers. Rep. Jonathan Singer, D-Longmont, attempted to run a bill earlier this year that would have delayed the implementation of HOV 3, but the effort didn’t make it out of committee.

“I think it’s unfair,” he said. “They are getting the short end of the stick. We should be encouraging carpooling not discouraging it.”

Singer said the need for HOV 3 is a symptom of the state’s lackluster transportation funding situation, which in large part depends on a gasoline tax that hasn’t been raised in more than two decades. More fuel-efficient vehicles haven’t helped in keeping revenues steady, prompting CDOT last month to announce a pilot program that would assess the feasibility of charging drivers by the mile for use of the state’s roads.

In the meantime, two-seat drivers such as Nate Derman said it all comes down to whether getting as many people as legally possible into a vehicle — even if that number is two — is a behavior that should be rewarded or not.

“My car is full. I shouldn’t have to pay,” Derman said. “On Jan. 1, you’re going to see a lot of two-seaters with a doll in the back.”