During the morning rush hour, commuters in cities across the East Bay climb into a stranger’s car. It’s part of casual carpooling, an informal ride-share system to save time and money while crossing the Bay Bridge. But a recent toll increase is causing turmoil in the casual carpool community.

In July, the Bay Area Toll Authority introduced congestion pricing for the Bay Bridge, raising fees from $4 to $6 between 5 a.m. and 10 a.m. and imposing a $2.50 toll for carpool drivers. Previously, carpoolers crossed the Bay Bridge for free.

The new carpool toll has users of the casual carpool system struggling to divide up the costs. Soon after the toll increase, internet message boards hosted heated discussions between drivers and riders who use the ride-share system.  Neither side is able to agree on what a shared ride across the bridge is worth. Some drivers say riders should contribute $1 each towards the toll, while some riders believe their presence is payment enough—drivers normally pick-up two riders to qualify for the carpool lane, which saves time and up to $3.50 off the toll.

The new toll has also affected traffic on the Bay Bridge. Since September 2009, more drivers are commuting before 5 a.m. and after 10 a.m. to avoid the higher congestion-priced tolls. And carpool traffic has dipped significantly, from a daily average of almost 18,000 cars to fewer than 14,000—a decrease of almost 25 percent.

We talked with commuters about the new toll at casual carpool meet-ups in Rockridge and North Berkeley. Most said that a contribution of $1 per rider is common. But there is still no agreement about who should broach the subject of payment, and payment systems still vary between cities.