The NSC’s data show that, most often (53 percent of the time), the driver of the car had forgotten a child was in the back seat. But 19 percent of the deaths occurred because children had been intentionally left in a vehicle, and 26 percent were attributed to children having gotten inside a vehicle on their own. To keep this latter situation from happening, safety experts say parents should make sure their children know that cars are not a play area and should keep all cars parked at their home locked at all times, with the keys out of children’s reach. Adults are advised to never leave a child alone in a car, an action deemed illegal in at least 19 states, and to put something you will need — a purse or employee badge, for instance — in the back seat so you will have to open the back door (and be reminded the child is there) before walking away. Apps and sensors are available that send alerts to a cellphone that a child is still in the car. The NSC also offers a free online course, at training.nsc.org/hot-cars. It provides information on the danger of vehicular heatstroke in children and includes preventive tips.