Across the country, a slew of new laws are going into effect.
Drivers in several states will need to learn some brand new rules of the road.
As of Sunday, it is illegal for drivers in California to hold a cellphone while behind the wheel.
Now, all devices must be mounted and can only be used for functions that require a simple swipe or tap.
In Illinois, bicycles now officially have the same right of way as cars.
The new legislation is named after Dennis Jurs, a veteran who was killed on his bike by a car that failed to yield.
And Boston drivers are starting off the new year by slowing down. To help reduce traffic deaths, the city's default speed limit is now 25 mph, down from 30 mph.
Gun owners in Missouri and California will be seeing some big changes, too.
Anyone 19 or older who owns a gun in Missouri can now carry it in public without training or a permit, so long as it's concealed.
On the other hand, California has made it illegal to sell most AR-15-style rifles with removable magazines or ammunition clips.
And recreational marijuana will be legal in a few more states — Nevada, Maine and Massachusetts.