There’s a high cost to driving while poor, according to a new report from East Bay Express, a Northern California alternative newspaper. The paper notes that traffic citation fines of $100 have risen to $500 as municipalities rely more heavily on fine collection to build revenue. Many low-income people can’t afford to pay. In the last eight years, 4.2 million driver’s licenses have been suspended because people have failed to pay fines or show up to traffic court. This effectively creates a painful spiral of inequality: People can’t drive, so they can’t get to work. Many lose their jobs.

The problem isn’t isolated to California. Across the country, fees and fines associated with traffic citations have steadily increased over the past several decades, according to a relatively new report by the Lawyers’ Committee for Civil Rights of the San Francisco Bay Area.

The problems associated with traffic courts and their role in driving inequality have surfaced in recent months, mainly after the death of Michael Brown, an unarmed black teenager in Ferguson, Missouri. Brown’s death triggered a U.S. Justice Department investigation that found Ferguson police officers were ordered to target the city’s mostly poor, black residents for traffic violations that few could pay. In 2013, the year before Brown’s death, Ferguson’s municipal court issued more than 32,000 arrest warrants for nonviolent offenses, mostly driving violations. Keep in mind that Ferguson has roughly 21,000 residents. Black motorists in Ferguson made up 67 percent of the population but 86 percent of those stopped by police.

The East Bay Express article helps detail the problem. Here are some key takeaways:

• An estimated 17 percent of adults in California have suspended driver’s licenses for missing a hearing or payment deadline.
• In Oakland, California, data shows that police stop black residents at disproportionate rates. People of color are more likely to get traffic citations and wind up in a court system that preys on low-income residents.
• Out of 66,000 people arraigned last year in traffic court, 68 percent pleaded guilty or no contest—meaning they didn’t attempt to fight the charges and agreed to just pay the fines.
• Legal aid groups have argued that the civil assessment penalties should go to the state’s general fund instead of the courts, so that judges don’t have incentives to issue the maximum $300 penalty and ignore a defendant’s inability to pay.