In the next four years, San Diego planning officials hope to break ground on several major transportation projects: A trolley line from Old Town to University City, carpool lanes along the southern portion of Interstate 805 and a widening of State Routes 94 and 76.

They’re among the $200 billion in projects the San Diego Association of Governments has planned through 2050. There are dozens of others, including wider highways, longer trolley lines and faster bus routes.

Those decisions will shape the way San Diegans move around the county in the coming decades, and whether it will be easier to hop on a bus or trolley or take the freeway.

But exactly how transportation planning officials have decided which projects to spend billions on — and when, and why — has been shrouded in secrecy. Their justification is detailed in complex models, formulas and data that few understand.

That’s drawn scrutiny from state Attorney General Kamala Harris, Gov. Jerry Brown’s planners and members of the California Air Resources Board, who all want Sandag to make those models accessible to the public.

Local transit advocates have long sought to dig into them to understand how Sandag makes its decisions, but the agency has resisted their requests to release the information.

Advocates had to hire lawyers to get Sandag to release the models at all. The agency relented, but even then only on the condition that the advocates not share them with anyone else and only use them in certain ways.

Harris called Sandag’s lack of transparency about its decision-making models “a crucial flaw” that “made it difficult or impossible for the lay public to determine for itself whether the information presented … is accurate and supported by substantial evidence.”

How Modeling Works

Transportation planners use complicated models to decide what types of projects to build.

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Take the new trolley line that will run to University of California, San Diego. Planners have to make assumptions about how many people are likely to ride it and how many fewer people will drive their cars as a result.

The answer isn’t easy. It’s likely to depend on how much money a person earns. And how far away he or she lives from work. And how much time the trolley is likely to save.

Beyond that, other factors came into play in deciding whether to build the trolley at all. Like whether the areas connected by the new line are expected to become regional job hubs.

And then planners’ formulas have to show how the new trolley will help meet state goals to reduce greenhouse gases.

To answer those questions, the agency has to make numerous assumptions. They all get programmed into complex formulas that help it decide how to design its transportation network so people can get around while still meeting state requirements to reduce those climate change-inducing gases.

Questioning Sandag’s Models

Transit advocates, like Move San Diego and others, have been trying to understand Sandag’s formulas for years. But the public agency has tried to keep that information secret, saying its models are proprietary — intellectual property it can’t release because of agreements with the contractors who developed it.

Last year, lawyers for local transit advocate Duncan McFetridge threatened to sue the agency, and it finally released the data. But the information was so indiscernible they had to hire a consultant to help them understand it. What they found troubled them.

They believe Sandag’s formulas make assumptions that allow the agency to justify highways over transit — reinforcing advocates’ chief criticism.

One of the assumptions they found is that poorer people are more likely to ride transit while wealthier people will not, even if the service is improved. Sandag’s model predicts that higher income residents will take just 4 percent of work trips on transit while lower income residents take 37 percent. The advocates argue that assumption allows Sandag to justify highway expansions by saying some people will just never ride buses or trolleys no matter how convenient it is.

They also claim Sandag’s model assumes San Diego will grow the same way regardless of whether the agency invests in highways or transit, not accounting for how transit might actually promote more compact development.

In an email, Clint Daniels, a Sandag planner, said the agency’s models had been extensively reviewed by federal transportation administrators. He said Sandag tries to account for how transportation will impact land use. And he said income is appropriate to consider when predicting transit ridership. Sandag had collected data showing more than half of transit riders had incomes under $25,000, and that transit use decreased as income increased, he said.

Advocates have tried to make the case that Sandag’s assumptions are exaggerated by pointing to areas like San Francisco County where the gulf between transit use by rich and poor is smaller, saying it can be narrowed in San Diego too if transit options are improved.

Why State Officials Care

As I wrote recently, San Diego is being watched across the state as it finalizes its transportation plan. It’s the first region required by a new state law to show how its plan will reduce greenhouse gas emissions during the next 25 years, by doing things like encouraging more transit and bicycle use and promoting denser development.

Its transportation models are a critical part of that, because they set the limits for what Sandag believes is possible. If it believes wealthy people aren’t likely to ride transit, it has to get them around another way. If it doesn’t account for how its transportation decisions will impact regional growth, it may not be motivated to aggressively use its transportation network to promote smart growth.

Chris Ganson, a planner in the Governor’s Office of Planning and Research, recently wrote to Sandag asking it to be more open with its models so the public could have a chance to weigh in.

“Models used in regional planning have become increasingly important in informing transportation and land use decisions. These decisions affect billions of dollars in infrastructure investments and influence regional and local growth patterns,” he wrote. “Transparency in the modeling system is, therefore, very important.”

At a recent hearing in Sacramento, Sandag director Gary Gallegos told the California Air Resource Board that the agency was working to develop models that are more accessible to the public.

He said the agency’s models will be available to the public by the next time it updates its transportation plan in four years.

Adrian Florido is a reporter for He covers San Diego’s neighborhoods. What should he write about next?

Contact him directly at or at 619.325.0528.

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Adrian Florido is a former staff writer for Voice of San Diego.

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