In just a few weeks, experts predict traffic on the Long Island Expressway is expected to get worse. 

That's because a federal program allowing electric vehicles into the express HOV lane is set to end. 

Many experts predict it will cause a shift in traffic patterns. 

"Losing this perk is going to hurt a lot of people"  

Under New York's Clean Pass Program, drivers of electric vehicles were allowed to travel in the high occupancy vehicle, or HOV, lane on the LIE, even if they were driving alone. 

Crews finished building the HOV lane back in 2005. About a year later, the Clean Pass Program was introduced, initially as a pilot. There are now almost 80,000 electric vehicles registered on Long Island, and nearly 50,000 of them are signed up for the program.  

The state Department of Transportation recently sent out thousands of notices to participants, saying "Congress and the president have not reauthorized this program," and "it will end on September 30th." 

Transportation experts predict the change will cause a mess on the highway since it will push those vehicles into regular traffic lanes. 

"Losing this perk is going to hurt a lot of people," Robert Sinclair of AAA said. "During rush hours, it will make for more traffic."

"I am not so happy"

Sustainable transportation advocates call it too abrupt of an ending. 

"There is capacity on the HOV lane and at some point, you'll run out and the program would have to end, but you could have changed what vehicles had access to it," said Rosemary Mascali, chair of the Drive Electric LI Education and Outreach Committee. "You could have said, starting in September, hybrids can no longer participate because you don't get as great fuel efficiency."

"This is worsening the idea and it's going to make the DOT rethink the whole idea of an HOV lane. Maybe they'd like to put it in places with more buses," said Marjaneh Issapour of the Renewable Energy & Sustainability Center at Farmingdale State College. 

Deer Park resident Peter Vanzandt owns an electric vehicle, and says it cut the time of his daily commute in New York City in half. That might not be the case very much longer. 

"Part of the reason why I bought the car was for that perk, so I am not so happy," he said. 

Supporters of the Clean Pass Program, like the nonprofit Renewable Energy Long Island, are calling for an extension "for further studies of congestion issues and the benefits for human health and the environment." 

CBS News New York spoke with some drivers who had mixed reactions. 

"Returning back to the original use of high occupancy is fine with me," Dennis Sullivan said. 

"I think it's a sad thing. We want to encourage people to use electric," Greenport resident Ann Plyler said. 

New York's DOT said it stands ready to continue the Clean Pass Program if Congress and the president move to extend authorization.