Car seats are not installed properly more than 50 percent of the time, according to the Department of Transportation.

According to a new study in the Journal of Pediatrics, 43 percent of all children killed in car crashes in the U.S. are not properly restrained or not restrained at all.

For our inspection, KARE 11 consulted Julie Philbrook, a registered nurse, certified child passenger safety instructor, and Trauma Prevention Specialist at Hennepin County Medical Center.

She provided the four must-dos for car seats.

1. Read your seat manual -- Sounds strange, but she says a lot of people don't, and each seat and car is different.

2. Seat strap tightness -- "I don't want to move it more than an inch side to side or an inch away from the top," she says.

3. Strap height -- Philbrook says the slot the straps come out of should be at or above the shoulder for front-facing seats and at or below the shoulder for rear facing seats.

4. The pinch test -- "I should not be able to take a pinch in the webbing," Philbrook says. If you can pinch the strap fabric together, it's too loose.

RELATED: Graco recalls over 25,400 child car seats

A list of places to get a free car seat check in Minnesota is available on the DPS website.