WASHINGTON - Alert passersby in a Philadelphia parking lot may have saved a life this week when they noticed an infant trapped in the heat of a locked car. The Good Samaritans, seen on cellphone video, called first responders who rescued the child, and took its parent into custody.

But with the United States entering the deep summer months, too many families have been less fortunate: a sobering 17 children have died of heatstroke in vehicles so far this year and likely more will come. An average of 39 U.S. children have died per year since 2003, according to a San Francisco State University study. Over half were simply forgotten by their caretakers.

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Today the Department of Transportation is urging new parents to remember these ways they can avoid a tragedy:

• Never leave a child alone in a parked car, even with the windows rolled down or air conditioning turned on. Air conditioning can fail, and cracked windows may not be adequate to protect a child whose body temperature rises three to five times faster than adults
• Always look in both the front and back of the vehicle before locking the door and walking away.
• Outdoor temperatures as low as 57 degrees can still be fatal over time. On an 80-degree day, a car can reach fatal levels in just 10 minutes.
• Think of some ways to remind yourself about your child in the back seat. Put something you always keep on you, like your cellphone or purse, next to them, to remind you to turn around before getting out. Have a cellphone with an alarm clock? Set an alert.
• Make sure their day care or school knows to call you if they do not show up. Or call your partner or spouse after you drop your child off with them to make sure you didn't forget.
• Never let children play in an unattended vehicle. Teach them it is not a play area.

At a Washington day care center this morning, a DOT demonstration emphasized the point. Under dark, overcast skies threatening rain, and a comfortable 75 degrees, a parked sedan reached 94 degrees within an hour. Transportation Secretary Anthony Foxx told families, day care workers and media that he wanted to erase the perception that such deaths are an accident that "happens to other people in other places."

"A lot of times [as a parent] you're tired. You're overwhelmed. You're stressed out. You've got lots of things to think about," he said, "and in some cases your mind just isn't functioning as sharply as you'd otherwise want it to."

"Parents just forget to look into the backseat, especially when their routines change, and bad things happen," he added.

Foxx was joined by a Reggie McKinnon, a father whose infant daughter died in such a tragedy when he forgot her for four hours after picking her up from a doctor's appointment and returning to work. He now says he honors her by educating others on heatstroke.

"Before [my] accident, every time I would read of a child dying in a parked car of heatstroke, I would ask, 'How could they forget their child? I would never do that. That only happens to people who are uneducated, drunk, drug addicts, not me,'" he said, holding back tears. "And I couldn't be farther from the truth."