Driving while black in California can be expensive, especially if you are poor.

According to a report by Back On the Road California, a consortium of social justice and legal groups, black drivers in the state are more likely to have their licenses suspended for failure to appear in court or failing to pay a ticket than whites. Black drivers are also more likely to be arrested for driving with a suspended license than whites for the same offense.

"Right now, California and many states around the country are using license suspension as a debt collection tool rather than a tool for public safety," said Elisa Della-Piana, the legal director for the Lawyers' Committee for Civil Rights in the San Francisco Bay Area, one of the groups that co-authored the report.

Statewide, 2% of all drivers have suspended licenses, the report found. But in almost all of the zip codes where blacks are more than 20% of the population, the license suspension rates were higher than the state average. Those zip codes were also some of the poorest in the state, researchers found. Blacks are also more likely to be stopped and have their vehicles searched by police compared with whites.

The researchers looked at several data sources, including the California Department of Motor Vehicles and the U.S. Census Bureau.

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Often drivers have had their licenses suspended because they cannot afford to pay a ticket they received for a lesser offense, said Della-Piana. That can have a "devastating" impact on low-income Californians who could lose their jobs if they are unable to drive to work, she said.

The fees and fines are also often compounded, creating an inescapable financial rut for those who cannot afford to pay. "The courts are using poor people as an ATM," Della-Piana said. "Something that starts out at $100 could easily end up being $800."

That's what happened to Reginald Cole, 47, an African-American truck driver who lives in Los Angeles. In 2012, Cole got a ticket for having a broken taillight that he said he could not afford to fix. When he went to court the judge told him, "Fix it or the price of the ticket goes up," Cole said. "They don't care."

When he did finally fix the light, his license had been suspended and his registration expired. But he had to keep driving in order to take care of his ailing mother and to see his children. The police continued to pull Cole over for his expired registration, and the costs continued to mount. He ended up owing $2,500 in fees, fines and tickets.

"We just call it driving while black," Cole said.

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Researchers also found racial disparities among those who are arrested for failure to appear in court for a traffic violation or failure to pay a traffic violation fine. In Los Angeles, blacks comprise 9% of the population, but they make up 32% of the arrests for those offenses. Meanwhile, whites make up 27% of the population, but comprise 12% of arrests.

In San Francisco, blacks are just 6% of the population but represented 49% of arrests for failure to appear in court or pay a traffic fine. That's compared to whites, who represented 41% of the population and 23% of the arrests for similar infractions.

The racial discrepancies for blacks and whites who were arrested for suspended license violations in each city were similar.

In Los Angeles, blacks comprise 9% of the population yet account for 33% of the arrests for that offense. Meanwhile, whites make up 27% of the population, but 15% of arrests. In San Francisco, blacks comprise 6% of the population but make up 46% of the arrests for suspended license violations. Whites in San Francisco make up 41% of the population and 40% of arrests.

Calls to the California attorney general's office, Los Angeles Police Department and the San Francisco Police Department were not immediately returned.