Last Wednesday, Mayor Jim Kenney signed a bill making Philadelphia the first major city to ban traffic stops for minor violations. The “driving equality” law presents a real opportunity to improve police-community relations and reduce dangerous encounters between officers and Philadelphia motorists. However, while the city’s decision to decrease these types of stops should be applauded, real change must happen at the state level.

The law, passed with a companion bill tracking data on vehicle stops, prohibits stops for seven low-level infractions — such as a broken taillight, or expired tags. These violations pose little risk to public safety, yet they often are why people get pulled over.

Low-level violations are so common that if you drive long enough on the road, you will commit one. This means that officers can essentially stop whomever they like. In many cities, officers use these low-level stops as an excuse to go “fishing” for other crimes.

Although we all commit these types of violations, we are not all equally likely to be stopped by the police. Black drivers are disproportionately targeted — sufficiently so that “driving while Black” is a part of everyday vernacular. Recent data, for example, showed that 72% of drivers stopped in Philadelphia are Black (though they only make up 42% of the city’s population). Many have compared fishing stops to other discretionary practices, such as “stop and frisk.”

It would be one thing if these stops actually did something to improve public safety. But only a tiny fraction of these stops turn up evidence of other crimes.

» READ MORE: Philly has become the first big city to ban minor traffic stops said to criminalize ‘driving while Black’

We know this because we’ve studied it. In 2017, the Nashville Mayor’s office and Police Department invited our team at the Policing Project at the New York University School of Law to evaluate the department’s use of traffic stops as a crime fighting tool.

Working with researchers from the Stanford Computational Policy Lab, we found that only a tiny fraction of stops — less than 1% — resulted in a gun charge, the discovery of an outstanding warrant, or an arrest for a more serious crime like robbery or burglary.

To the department’s credit, they quickly recognized that there were much better ways for their officers to spend their time. In the two years after the study, the department cut stops by more than 80%. The department now emphasizes that traffic enforcement should focus primarily on traffic safety. And it relies on more targeted strategies — often in collaboration with residents — to address violent crime.

Philadelphia’s new law is good, commonsense legislation that can help to reduce racial bias in traffic stops. That’s why it gained the support of the Philadelphia police department. Low-level traffic stops create flashpoints of confrontation that too often lead to devastating outcomes for police and motorists. They erode trust in police, very rarely yield any useful crime-solving information, and divert precious police resources from solving real crimes.

The problem is that the law’s power stops at Philadelphia’s borders. With hundreds of thousands of individuals commuting into and out of Philly everyday, a state-wide policy on traffic stops would have a much greater impact. Pennsylvania also has more police agencies than any other state, making a unified approach across its 1,117 agencies a necessity.

What is needed is a comprehensive statewide statute, like the one we at the Policing Project drafted. Our statute would prohibit stops for the most common low-level infractions. It would limit officers’ ability to go fishing for other violations. And importantly, it would require agencies to collect demographic data on all stops, searches, and arrests, so that communities can better understand who officers are stopping and why. A number of states, including Virginia and Connecticut, have already adopted measures along these lines.

Philadelphia has taken the first step, Pennsylvania lawmakers must take the next one.

Nila Bala is a senior staff attorney at the Policing Project at New York University School of Law. Maria Ponomarenko is a professor at the University of Minnesota Law School, and is co-founder and counsel at the Policing Project.