A new study of San Francisco's high occupancy vehicle (HOV) lanes has revealed something disturbing: more congestion. According to researchers at UC Berkeley and Cal State University, East Bay, in a 100 mile sample section of freeway, HOV lanes have counter-intuitively led to an increase in traffic congestion.

The study utilized data collected from sensors embedded in the pavement over 4.5 years between 2001 and 2005. As San Francisco's HOV lanes are only active for 8-10 hours per day, traffic could be measured both with and without the restriction in place, allowing for the comparison.

What they found was that not only was there no increase in carpooling, but that that when HOV lanes were 'active',  traffic capacity decreased by 20-percent by increasing congestion on other lanes. A report from 2005 also noted that  in areas where HOV lanes are not separated from general traffic, accident rates increase by some 50-percent.

[Sources: TheNewspaper.com, CalAcademy.org]