It was one of those quirky Bay Area cultural practices that made living here unique -- the casual carpool.
After the Loma Prieta quake, and during the dotcom heyday, drivers looking to get to work a little faster would pick up strangers near BART stations across the East Bay for rides across the Bay Bridge.
The incentive? Besides use of the carpool lane, bridge tolls for vehicles with multiple passengers were waived.
But that may come to an end as Bay Area bridge officials consider charging carpoolers $2.50 during rush hours -- still cheaper than the increase to $6 proposed for individual drivers, but enough to upset the delicate free-ride dynamic of the casual carpool.
Would riders split the $2.50 charge four ways? Or would profiteering drivers start asking riders for a buck apiece?
Meanwhile, BART ridership is also down, while that agency is also looking to raise fares to cover the deficits that dovetailed with decreased ticket sales.
And while the safety of the Bay Bridge is still questionable, today's derailment of a BART train can't have have made that option any more attractive.
In the end, despite the toll hikes and the self-righteous environmentalist posturing in the region, the marginal cost of commuting alone in your gas guzzler is going down.
So, save for a spike in gas prices or more transit mishaps, the casual carpool may be going the way of the San Francisco garter snake, itself a victim of the region's freeway-first transportation planning.