Making sure children are properly buckled up in the car is the single biggest thing that could be done to save young lives in car crashes, according to a new study that looked at traffic deaths state by state. 
 
 The researchers also found that some states do much better than others when it comes to children's survival in car crashes. 
 
 Using data from Department of Transportation reports on motor vehicle accidents involving children, along with information from the U.S. Census on how many children live in each state, researchers from Brigham and Women's Hospital were able to compare death rates state by state. Their study is published in The Journal of Pediatrics. 
 
 Between 2010 and 2014, the data showed that 18,116 children were involved in fatal motor vehicle crashes and 15.9 percent died. 
 
 Rates were calculated as the number of deaths in each state for every 100,000 children under the age of 15. 
 
 The five states with the lowest rates of death: 
 
 Massachusetts 0.25 
 
 New York 0.29 
 
 New Jersey 0.32 
 
 Washington 0.33 
 
 Rhode Island 0.33 
 
 
 
 The five states with the highest rates of death: 
 
 West Virginia 2.16 
 
 Montana 2.23 
 
 Alabama 2.71 
 
 Wyoming 3.06 
 
 Mississippi 3.23 
 
 
 
 "We looked at a ton of variables: characteristics of kids, state policies, locations of crashes. Being unrestrained or inappropriately restrained was the biggest factor in more kids dying," said the study's lead author Dr. Lindsey L. Wolf, a general surgery resident at Brigham and Women's Hospital and a research fellow at the Center for Surgery and Public Health there. 
 
 "In severe car crashes, 20 percent of kids nationally, across the board, were not restrained or were misrestrained," Wolf told CBS News. 
 
 In Mississippi – the state with the worst track record on seatbelts – 38 percent of children who died in crashes were not restrained or were improperly buckled. On the flip side, only 5 percent of children in Washington state who died in accidents were not restrained properly. 
 
 Seatbelt education efforts have been pretty strong in recent years, said Wolf, including updated car seat recommendations for children published in 2011 by the American Academy of Pediatrics, so the findings came as somewhat of a surprise to the authors. 
 
 "The death rates were way higher than we expected them to be," Wolf said. 
 
 The states with the highest child fatalities due to car accidents tended to be more rural. For example, 92 percent of crashes in Montana and 89 percent of crashes in Wyoming occurred on rural roads. 
 
 "There's information that generally these roads may not be as well-maintained and they may be less well lit and more windy – some characteristics that may lead to these severe crashes," said Wolf. 
 
 Parents living in rural areas need to be aware that the risks there are higher and that they're driving as carefully as possible, and to make sure children are buckled up correctly in car seats, according to their size and weight, Wolf added. 
 
 Motor vehicle injuries are a leading cause of injury and death among children, but about 232 childrens' lives could be saved each year if little ones were appropriately restrained while traveling in cars, the study authors said. ||||| FILE - In this June 18, 2014, file photo Cobb County police investigate an SUV where a toddler died near Marietta, Ga., when the father forgot to drop his child off at day care and went to work. A proposed... (Associated Press) 
 
 A proposed law that would require carmakers to build alarms for back seats is being pushed by child advocates who say it will prevent kids from dying in hot cars. 
 
 The law also would streamline the criminal process against caregivers who cause the deaths — cases that can be inconsistent but often heavier-handed against mothers. 
 
 The latest deaths came in Arizona on triple-digit degree days over the weekend, with two baby boys found forgotten in vehicles in separate incidents. 
 
 More than two dozen child and road safety groups are backing the U.S. Senate bill introduced last week aimed at preventing those kinds of deaths by requiring cars to be equipped with technology that can alert drivers if a child is left in the back seat once the vehicle is turned off. It could be a motion sensor that can detect a baby left sitting in a rear-facing car seat and then alert the driver, in a similar way that reminders about tire pressure, open doors and seat belts now come standard in cars. 
 
 "The technology would help because if you're in a vehicle, your child is in the back seat, and you ignore that alarm: Go to jail. Do not pass go. You had a chance," said Janette Fennell of the advocacy group Kids and Cars.org. "You talk to any of the judges, they'll tell you, they're beyond the hardest things they have to deal with." 
 
 Police say 1-year-old Josiah Riggins was in the car for hours Saturday, discovered dead only after his father drove roundtrip, twice, between their suburban home and a Phoenix church to drop off the mother and a sibling. 
 
 Zane Endress, who was 7 months old, died Friday in Phoenix after being left in the car in the driveway at home, as his usual daycare drop-off routine was lost by his grandparents. 
 
 "A simple sensor could save the lives of dozens of children killed tragically in overheated cars each year, and our bill would ensure such technology is available in every car sold in the United States," bill sponsor Sen. Richard Blumenthal, a Democrat from Connecticut, said in a statement. "It can take mere minutes on a hot day for a car to turn into a deathtrap for a small child." 
 
 No charges have been filed against the caregivers in either Arizona case, as police say the death investigations are underway. Detectives will determine criminality based on the caregiver's neglect, intent and mindset, while also being sensitive to the family's deeply felt loss of a child, Phoenix police Sgt. Mercedes Fortune said. 
 
 "Those are the very difficult questions. Each case is different. I can't tell you there's a set answer for any case because there really isn't," Fortune said. 
 
 Kids and Cars, which has tracked more than 800 children who have died in this way since 1990, said criminal cases vary greatly, even when the circumstances are identical. Fennell said 90 percent of cases involve pure accidents, most likely a child forgotten by an adult. 
 
 In this month alone, a Tennessee couple was charged in the death of their 11-month-old daughter. A nearly 2-year-old boy was found dead in his father's BMW in south Florida. 
 
 The nonprofit's analysis shows charges are filed about half of the time, though very rarely are the parents found guilty objectively because it was proven that the child was left behind to be harmed. There is also a noted gender bias: Mothers are more often charged than fathers, and among the convicted, women caregivers receive longer prison sentences than men, the study found. 
 
 "It's also a defense mechanism. If I make monsters out of these people, then it could never happen to me," Fennell said. 
 
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 Follow Sally Ho at http://twitter.com/_sallyho
– A new study published in the Journal of Pediatrics found ensuring children under 15 are properly restrained—or wearing seat belts at all—could save about 232 lives every year. Researchers found 20% of children who died in fatal car crashes between 2010 and 2014 weren't buckled in or were improperly restrained, NPR reports. Of the more than 18,000 children involved in fatal car crashes in those years, 15.9% died. The biggest factor in those deaths was whether the children were properly restrained. Other factors included rural roads, which increased the likelihood a child would die in a car crash, and red light cameras, which decreased that likelihood. The study found child fatality rates varied widely by state, which makes sense as seat belt laws, public information on car seats, rural roads, and the use of red light cameras also vary widely by state. More than half of all children who died in a car crash lived in the South. The highest rates of death were in Mississippi, Wyoming, Alabama, Montana, and Virginia, CBS News reports. The lowest were in Massachusetts, New York, New Jersey, Washington, and Rhode Island. In Mississippi, 38% of children who died in a fatal car crash weren't restrained properly or at all. The study's authors advocate for stronger seat belt laws and better public information—potentially at the federal level—to protect children in car crashes.