Rush hour delays on the Bay Bridge could more than double if voters reject a pair of transit taxes on the November ballot, according to a report by SPUR, the nonprofit think tank that has endorsed both measures and largely spearheaded the regional one.

Called, “Bumper to Bumper,” the analysis predicts cascading effects if three major Bay Area transit operators were forced to eviscerate service. The projected impacts on traffic alone are all but apocalyptic. SPUR describes a future in which thousands of erstwhile train or bus riders revert to driving, further straining freeways that are already jammed. Travel times across the Bay Bridge could stretch from 30 minutes to more than an hour during the peak morning commute, and from half an hour to 73 minutes in the evenings.

Other critical choke points like the Caldecott Tunnel on Highway 24 could also become traffic purgatories. Trips through the Caldecott could lengthen by 20 minutes for those going westbound in the mornings and 27 minutes eastbound at dusk. Anyone driving along Highway 101 from the Peninsula to San Francisco may contend with gridlock along Hospital Curve, swelling times by eight minutes for those heading north in the morning and 12 minutes going south in the evening. Interstate 680 in Concord and Walnut Creek could become another misery point, with drivers spending an extra 15 minutes crawling through the worst snarls in the mornings, and an additional 20 minutes in the evenings.

It’s the bleakest and most detailed picture to date of how the region might look if BART, Muni and Caltrain were severely gutted.

“I think in some ways you could think of this as the best-case scenario,” said Laura Tolkoff, author of the report and transportation policy director at SPUR. “And unfortunately, the best-case scenario is pretty ugly.”

Each of the three big transit agencies is navigating a deep financial deficit, with ridership slow to return after the pandemic and COVID emergency funds mostly drying up. BART’s budget hole could widen to between $300 million and $400 million a year, while Muni is trying to patch an annual gap that could balloon to $430 million in five years. Caltrain’s projected shortfall hovers at $75 million a year, though it could also grow if the Peninsula rail system hits a death spiral.

To stem the bloodletting, policymakers and transit advocates have placed two bailout measures on the November ballot. Proposition RTM is a five-county sales tax to be shared among many operators; Proposition H, meanwhile, is a parcel tax dedicated for Muni in San Francisco. Earlier this year, as the campaigns for these taxes got underway, the three main agencies released contingency plans for station closures and route reductions if the measures fail. BART would shutter up to 15 stations and run trains every half hour. Caltrain would close more than a third of stations. Muni would slash up to 20 bus lines.

Opponents of transit funding measures have accused supporters of exaggerating the potential collapse of these public transportation systems. Some even suggest the transit agencies have dramatized their contingency plans to help advance an agenda.

But SPUR used these plans as the basis for “Bumper to Bumper” — with some caveats. Staff at the nonprofit and their consultant, the engineering and infrastructure firm Jacobs, extrapolated a few crucial details for their premise. BART and Caltrain both relayed how many train stations they would have to shut down, but did not confirm which ones would be on the chopping block. SPUR and Jacobs assumed the lowest-ridership stations would be first to go, a notion that they claim makes the findings “intrinsically conservative,” the report said. Closures of busier stations would have much greater influence on traffic.

Although the East Bay bus system AC transit also released a closure plan to stabilize its budget if the regional tax falters, it came out too late to be fully considered in “Bumper to Bumper,” Tolkoff said.

Anticipating how people’s habits would change if their preferred transit modes were no longer available was an art as well as a science. SPUR and Jacobs evaluated income demographics around stations and bus stops to determine what share of people had latitude to work from home or commute on flexible schedules. They also took into account distances to the next available station and added wait times, trying to assess whether these new inconveniences would be enough to lure people into their cars. In all likelihood, commuters would make rational decisions based on the route they had to take. Many would prefer waiting a few minutes longer on a BART platform over slogging for an hour on the Bay Bridge.

With all these factors in play, the SPUR and Jacobs forecast that 56% of riders at end-of-the-line stations would shift to driving, as would 30% of people boarding trains at other closed stations, and 25% of people at stations that stay open but suffer reduced service.

While “Bumper to Bumper” tried to depict traffic on the region’s main freeway bottlenecks in granular detail, it did not capture the spillover to roads and arterials as people drive to stations that are farther away from their homes. If transit becomes generally less appealing then people would also stop using it for small trips, which could result in nuisance traffic throughout the day.

And snarled roads or freeways are but one aspect of the human toll we could see next year absent both tax bailouts, Tolkoff said. Other ramifications include heightened demand for parking in neighborhoods around BART or Caltrain stops that remain open, which in turn would mean more cars circling the blocks. Displaced riders would have to pay about $3,300 a year, on average, in additional costs for parking, bridge tolls and vehicle wear-and-tear, the report maintains. That’s “a pretty large amount of money for many households to absorb,” Tolkoff said.

Some families might buy another car. Commuters who don’t own vehicles may wind up spending prodigiously on ride-hails or relying on friends and family for rides. A wide swath of Bay Area residents would face serious challenges getting to work every day.

On top of all that are the environmental costs. Putting all those cars on the roads would generate 184,000 metric tons of carbon dioxide each year, the report concluded. That’s roughly equivalent to clear-cutting 219,000 acres of forest or a third of Yosemite National Park.

If a death spiral kicks in, advocates believe the effects would compound as more stations close and more buses are suspended. This chain of events is a bit like massive organ failure: Transit agencies pare back service, which drives riders away, which lowers fare revenue, which prompts more cuts. “Bumper to Bumper” illustrates the phenomenon with looping blue arrows that form a circle of doom: “incredibly difficult — and perhaps impossible — to reverse.”

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