Drivers in Minneapolis and St. Paul will have to slow down to 25 miles per hour on arterial streets and 20 miles per hour on residential streets starting this year, under new speed limits unveiled Thursday.

Leaders in both cities celebrated the lower speed limits in an event held in pouring rain on the municipal border line in the Prospect Park neighborhood. The cities proposed the lower speed limits last year as part of their effort to reduce traffic-related deaths and injuries and make streets safer for cyclists, pedestrians and drivers.

"There is nationally collected data that tells us that slower is safer," Minneapolis Public Works Director Robin Hutcheson said.

Whether signs alone are enough to change driver behavior or whether it will take more warnings and speeding tickets remains an open question.

Public works crews will put up the new signs — more than 1,000 in all — on arterial streets beginning Thursday. The speeds for all city streets should be changed by October, Hutcheson said.

Instead of speed limit signs on every residential street, signs at entry points to both cities will state the limit is 20 mph unless otherwise posted.

A few city streets will remain at 30 or 35 mph. Others that are 10 mph, such as alleys and Nicollet Mall, will not change, Hutcheson said.

Legislators gave local governments the authority to set speed limits on city-owned streets last year. Speed limits on state and county roads will not change.

Lowering the speed limits is a "radical move that is going to change the way our streets feel," St. Paul City Council President Amy Brendmoen. She noticed how slow the drive felt as she practiced driving under the new speed limits at night when other cars weren't around.

The change will require all drivers to change their behavior, Brendmoen said.

"Those five miles and 10 miles an hour make a big change," she said. "It's going to require all of us to think and act different."

At Thursday's event, Minneapolis City Council President Lisa Bender acknowledged the advocates who pushed both cities to lower speed limits, many of whom were there holding blue "20 IS PLENTY" signs.

"Reducing our speed limits in Minneapolis and St. Paul will save lives," Bender said. "Everyone should slow down; you'll get where you need to go and all of our communities will be safer and better for it."

Minneapolis Mayor Jacob Frey touted the lower speed limits as a win for local control, for parents whose children play on sidewalks and streets and for people without cars.

"We're thrilled with the direction this has taken," Frey said to the crowd. "Because of what we're doing here today, families across Minneapolis can quite simply feel safer."

The changes follow similar action by cities across the nation, including New York City, Portland, Seattle and Boston.

One Minneapolis council member questioned how the city planned to enforce the new speed limits. Last week, the council's public safety committee voted against applying for a $1.3 million federal grant that would have gone toward hiring 10 officers to focus on traffic enforcement.

Council Member Linea Palmisano, who sits on the committee and voted to apply for the grant, intends to revisit the issue at Friday's council meeting. She said another council member who voted against the grant application has since had a change of mind, without identifying who.

Without enforcement, speed limits like those unveiled Thursday are toothless, she said.

"I share my colleagues' concerns about ways we need to change policing across our country; I think the big difference is that some see it as we're going to restrict and take away your resources until you clean up your act, and I don't see that as a way of improving a department full of first responders," she said. "I don't see how you transform something without any additional investment."

Said Hutcheson: "We don't have to wait for additional enforcement to be in place to reduce speed limits now." Research found that drivers in Seattle and Boston still slowed down to the new speeds without any changes in traffic enforcement, she said.

The Minneapolis Police Department, she added, is leading a work group talking about how enforcement would be handled "in a very equitable way."

At Thursday's event, Minneapolis and St. Paul council members gathered underneath the first speed limit sign to be changed, on the northwest corner of SE. Franklin Avenue and SE. Emerald Street. They cheered as they pulled down the 30 mph placard to reveal the new 25 mph limit.

Five minutes later, a St. Paul police car blazed along Franklin with its flashers on, pulling over an SUV driver who had just crossed the intersection. A bicyclist with a two-wheeled trailer in the back rode past the scene.

Staff writer Libor Jany contributed to this report.