High Occupancy Lanes are intended to encourage carpooling, speed up traffic and improve air quality.
But a UC Davis professor of environmental science and policy says his research proves otherwise.
"My studies all show that that increases sprawl and emissions in air pollution."
Bob Johnston has studied HOV lanes for 15 years and uses computer modeling programs. He says carpool lanes allow people to live farther from work.
"When you run an urban model what you discover is that if you build freeways you get more sprawl then you get more travel on the freeways so you need more freeways."
He says more money should be spent on transit systems that support compact urban growth in the center of the region.