The Chicago City Council voted overwhelmingly Wednesday to decriminalize marijuana possession, joining a wave of states and big cities that have opted for fines instead of arrests for small amounts of the drug.

Starting Aug. 4, police can issue tickets of $250 to $500 for someone caught with 15 grams or less of pot — the equivalent of about 25 cigarette-sized joints. Given that more than 18,000 people are arrested for pot possession in Chicago each year, the new law could generate millions of dollars for the city.

The push for pot tickets marks the latest in an increasingly long line of Mayor Rahm Emanuel's maneuvers to find new sources of money that largely rely on penalizing people who run afoul of the law. The mayor counted on bad behavior to balance his first budget, anticipating that the city would raise $26 million in increased fines for such offenses as failing to cut high weeds, not feeding parking meters and driving with a suspended license.

This fall, cameras are expected to begin clocking motorists who speed on Chicago streets, resulting in tickets of up to $100 and tens of millions of dollars for the city. Emanuel framed that controversial plan as a way to leverage technology to better protect children near schools and parks.

Like the speed-camera plan, Emanuel insisted Wednesday that the marijuana fines aren't about the money.

"It's not about revenue, it's about what (police officers) were doing with their time," the mayor said. "The only revenue I'm interested in, I don't want to be paying for these officers time and a half to sit in a courtroom for four hours on something that 80 to 90 percent of the time will be thrown out and everybody, both the residents and police officers and judges, already knows the outcome."

In making the case for the city's new approach, police Superintendent Garry McCarthy said charges are dropped against the "vast majority" of people arrested for possession of small amounts of marijuana. And each arrest takes up to four hours of police time, compared with about half an hour to issue a ticket and test the confiscated weed.

McCarthy estimates that the new ordinance will free up more than 20,000 hours of police time, the equivalent of about $1 million in savings.

When marijuana possession cases are dismissed, the city collects no cash.

Emanuel's administration refused to say how much it anticipates raising. But based on the more than 18,000 arrests made for small possession in the past year, the city stands to haul in anywhere from $4.5 million to $9 million. The city's take depends on the amount of the ticket officers decide to write and how many people actually pay what they owe.

Police officers would continue to arrest people caught smoking marijuana or carrying it on park or school grounds. Authorities also would arrest anyone younger than 17 caught with pot or anyone they believed was trying to sell the drug.

Emanuel changed his original proposal to appease aldermen concerned that the city was sending the message that it was going soft on pot. Violators could be required to do community service. Those ticketed could be forced to take part in drug awareness or education programs. And the city still could impound offenders' vehicles.

"All of us have some internal conflict with what we're doing. ... Head-to-heart conflict. I think we did appropriate dialogue, debate, discussion, exchanging ideas and improving an ordinance from beginning (to) end," Emanuel said after the vote.

"This is one piece of correcting what I think has failed year in and year out," he added.

Before the 44-3 vote, several aldermen said African-American and Latino communities are disproportionately affected by the city's current policy to arrest people who possess small amounts of marijuana.

"If you had been white and privileged, marijuana has already been decriminalized," said Ald. Howard Brookins, 21st, who voted for the measure. "The only people arrested for these crimes have been black and brown individuals. ... This is a way to potentially level the playing field."

Currently, people convicted of possession face a misdemeanor charge punishable by up to six months in jail and a $1,500 fine.

Ald. Ameya Pawar, 47th, said the new approach will give officers the ability to fight more serious crimes.

"We need to distinguish between people who are part of criminal enterprise and people who are casual users," Pawar said.

Aldermen who voted against the measure expressed concerns about the message it would send to children. Ald. Roberto Maldonado said 15 grams is a significant amount of marijuana and he worried that the new policy would lead to a spike in public use of the drug.

"With the adoption of this ordinance, many of those thugs will perceive and misinterpret the law that it is a license to smoke marijuana in public," said Maldonado, 26th. "That's why I cannot come to terms to vote for this ordinance."

Ald. Edward Burke, 14th, an influential alderman who was among the first to voice concerns about the change, said Wednesday that his "skepticism has turned to support."

"We all come to this debate with different life experiences," said Burke, who noted that although his generation did not widely smoke pot, he is the foster parent of a former "cocaine baby" and he's witnessed firsthand the devastating effects of drug use.

Citing figures he said were provided by the Police Department, Burke said that among the arrests made for marijuana possession in the past year, more than 16,000 of them were of African-Americans.

"Just as I don't want to send the wrong message to kids, I also don't want it to be the case that young Walter or young Travis are going to be 16 times more likely to get locked up in the city of Chicago than some kid from Sauganash or Beverly," Burke said while looking at Ald. Walter Burnett, 27th, and referring to his own son, Travis.