Nissan is adding Rear Door Alert to more vehicles, helping make sure that drivers don't accidentally forget the most important things in the back seat.

"The idea was inspired when I accidentally left a pan of lasagna in the back seat of my car overnight," said Nissan engineer Marlene Mendoza, one of the two engineers credited with the idea for the feature. "The worst thing was the car smelled for days, but it made me ask myself, 'What if I left something far more important back there?’" It's an occurrence that can be tragic. Canadian figures aren't available, but US non-profit National Safety Council says that an average of 37 children die in hot cars each year in that country.

Even at 15 degrees outside, the back seat of a car can heat up to 43 degrees, according to the NHTSA. A change in daily routine or just a lapse of concentration can mean a child is left in that hot back seat.

Rear Door Alert is standard on the 2018 Nissan Pathfinder. It's a simple system that monitors the opening and closing of the rear door. If you opened the back door before you start your trip, but don't open it during the trip, the vehicle will alert you. Once the vehicle is in park and the ignition is turned off, the system will give you an alert on the dash. Ignore it, and the vehicle will start honking the horn to let you know that there might be something in the back seat you need to check on.

Nissan is the first automaker to add the horn to the rear door alerts. "By drawing attention back to the vehicle while the driver is walking away, the honking alerts you to recheck the back seat in addition to visual or interior audible alerts," said Mendoza.

For model year 2019, Nissan is adding Rear Door Alert to eight more models, including the Rogue, and the Altima. By 2022, Nissan plans to have RDA standard on all four-door trucks, sedans, and SUVs. It might only remind you that your 480-pack of toilet paper from Costco is back there, but it could also save a life.