Slower Long Island Expressway predicted as Clean Pass vehicles exit HOV lanes this week

Solo commuters on the Long Island Expressway should brace for more traffic congestion starting Wednesday while carpoolers can expect faster speeds as the Clean Pass program comes to an end, experts told Newsday.

The program, which grants exemptions for zero- and low-emission vehicles in high-occupancy vehicle lanes, stops Tuesday night because the federal government did not renew permission for New York and 14 other states to continue their programs. Beginning Oct. 1, only carpoolers will be able to use the HOV lanes during rush hours — no matter if they're fuel- or battery-powered.

There are currently over 160,000 electric vehicles and plug-in hybrids on Long Island and in New York City, but about 48,000 vehicles are registered with Clean Pass, according to the New York State Energy Research and Development Authority and the Department of Motor Vehicles. It is unclear how many Clean Pass vehicles regularly use the LIE, which daily handles about 180,000 vehicles across all lanes in both directions at the Nassau County-Queens border, where the HOV lanes begin. The lanes stretch 40 miles to Medford.

In the short term, the impact on traffic will depend on how strictly the change is policed, but in the long term, it may depend on whether people adapt by sharing rides, according to Michael Shenoda, a professor of traffic engineering at Farmingdale State College.

"If you take vehicles out of the high-occupancy lane and put them in the other lanes, then traffic is just going to naturally increase in those other lanes, given no other change," he said. Over time, though, "carpooling may start to look more attractive again" if the HOV lanes speed up relative to the regular lanes.

Robert Sinclair, spokesman for AAA Northeast, said except carpoolers, other LIE users should leave extra time to get to work beginning Wednesday.

"Everybody's going to get slowed down, not just the ones with the Clean Passes that no longer have access," he said.

In letters sent to Clean Pass holders in August, Gov. Kathy Hochul and the state Transportation Department blamed the Trump administration for ending the program, which started in 2006. But some clean-energy advocates said the program's days were numbered anyway, given increasing congestion in the HOV lanes as more electric vehicles used them. Under federal law, once HOV-lane traffic slows past a certain threshold — defined as a 45-mph minimum-average speed 90% of the time over 180 consecutive days during peak hours — the lanes must revert to only carpooling.

State Department of Transportation spokespersons declined to answer repeated inquiries about average speeds in the HOV lane, only saying they currently "met federal standards," and did not answer questions about how the end of the program may impact traffic flow.

Ending the program "may be very rational and logical, or it could be more [based on] other considerations. It's difficult to tell which one is which without seeing the numbers," said Anil Yacizi, a professor of traffic engineering at Stony Brook University.

The immediate effect of ending Clean Pass on traffic congestion will depend partly on how quickly and strictly it’s enforced, according to Shenoda, who estimated that even before the change, violators made up 5% to 10% of HOV lane users. Elsewhere in the country, the proportion of HOV lane violators varied from 1% to 43%, according to estimates in a 2008 report commissioned by the Federal Highway Administration.

Spokespersons for the Nassau and Suffolk county police departments told Newsday they plan to enforce the new HOV lane rules.

The long-term traffic impact of ending Clean Pass may depend on whether it convinces more drivers to carpool — though Shenoda said there is not strong evidence that HOV lanes actually persuade drivers to make the switch.

The first 12 miles of the LIE’s HOV lane opened in 1994, yet the proportion of carpoolers on Long Island actually declined between the 1990 and 2000 censuses, from about 12% to 11.2%. In 2024, carpoolers made up about 10.8% of Long Islanders who reported commuting by car, truck or van, according to the American Community Survey.

Still, it’s possible that carpooling rates might have fallen even more if the HOV lanes never existed, Shenoda said. It’s also possible that as Clean Pass ends, some drivers will switch to public transit.