DENVER -- Starting in January, a third person will be needed to use the carpool lanes on Colorado highways without being charged.
The HOV requirement will change to HOV 3+, or a driver plus two passengers, on Jan. 1, the Colorado Department of Transportation said.
"HOV 3 ensures that those lanes remain free-flowing now and into the future, so that those who choose to ride the bus, pay a toll, or carpool always have a reliable and faster trip," the CDOT website states.
"In addition, getting more people into carpools with HOV 3 reduces overall congestion and vehicle emissions -- a good thing for a state with a growing population."
CDOT released a statement saying it is working to help drivers find an additional passenger to carpool or use a different mode of travel, such as transit, and other options.
CDOT will also be making the switchable HOV transponder free to drivers who will only carpool, officials said.
The decision to increase the number of passengers needed to use the HOV lanes was made in 2013.