CAMBRIDGE (CBS) — On Thursday, drivers in Cambridge will be told to slow down, as the city drops speed limits on municipal-owned streets from 30 miles per hour to 25.

The change comes after the passage of the Municipal Modernization Act this summer, which allows cities and towns to drop speed limits without a traffic study. As more municipalities take advantage of the change in law, Civil Engineering Professor James Lambrechts of  Wentworth Institute of Technology said decreasing speed will likely increase safety.

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“You’ve got bicycles out there, we’ve got bike lanes. You have to be careful about bikes because they weave in and out of that bike lane and don’t pay a whole lot of attention to traffic coming up from behind them,” Lambrechts told WBZ NewsRadio 1030’s Ben Parker. “You’ve got people crossing crosswalks and not really looking both ways. Now they’ll be able to see the car coming because it’s not coming as quick so people crossing the crosswalks have a better chance of getting across.”

In addition to Cambridge, Somerville dropped its speed limits last month and Boston speed limits are set to drop Jan. 9. In all three cases, speed limits would go from 30 to 25 miles per hour, unless otherwise posted.

New speed limits aren’t a set it and forget it situation, though. Towns will likely have to take a few steps to ensure things are going smoothly.

“The towns will have to put some enforcement behind this, and one thing I’ve seen in some towns are these little flashing lights that have a sensor and they tell you how fast you’re going. They say the speed limit is 25 and you’re going 30. That tells the driver right away, I’m going too fast. Perhaps they continue to go too fast but at least they’ve been given a visual,” Lambrechts said. “That’s the light side of enforcement. Of course, towns could have their police departments go out with their radar gun and pick people up for going over the 25 speed limit.”

Lower limits could also mean increased traffic, Lambrechts said. If congestion gets too bad, he added, towns should consider bumping speed limits on those streets up a notch.

“The one thing you should consider in doing this is will it have a negative impact on the traffic flow, will it give you more congestion?” Lambrechts said. “Do you have a street that’s going to become really backed up, really slowed down because you’re dropping the speed limit? If you’re in a thickly settled area maybe it doesn’t make any difference. But the towns do need to consider all the different aspects on how much volume they’ve got going on certain streets. It’s sort of a big study where we’re going to change something and then study the impact rather than thinking about what is going to be and doing that study ahead to time.”

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WBZ NewsRadio 1030’s Ben Parker reports