The report, Paying More for Being Poor, makes the case that the traffic system is discriminatory because of racial profiling by police officers: Black drivers are more likely to be pulled over for no cause.

Elisa Della-Piana, the legal director of the Lawyers’ Committee for Civil Rights, also makes a case purely on income grounds.

“Many folks see that we have an unfair system,” she said. “You have two people, each of whom rolled through a stop sign. One mails in a check. The other doesn’t have enough money and experiences license suspension, arrest, job loss. Those are disproportionate consequences.”

Mr. Hertzberg’s proposal would not be as radical as the system in Finland, where traffic fines for wealthy people can climb into the tens of thousands of dollars.

The California bill puts the burden on the courts to determine if a violator is “indigent” and if so, assess a lower fine based on income. Passage of the bill will depend on budget negotiations in the coming weeks.

Mr. Hertzberg said there was concern that court revenue would decline too much, but he said the ultimate goal was to lower fines for everyone.