Cell phones are just one of the many distractions that challenge drivers.

The last thing Ashley Umscheid did before her pickup flipped end over end, throwing her into a ditch, was tap a single letter on her phone: K.

Short for OK, it was a reply to a text from her older sister on that spring day in 2009.

Amanda Umscheid didn’t receive the message, and she never got to talk to Ashley again. The 19-year-old Kansas State University student died a few days later from injuries she suffered in the one-vehicle wreck near Manhattan, Kan.

Amanda Umscheid, 29, has spent much of the three years since telling her sister’s story. She wants teens to understand that texting while driving is not worth their life, or the anguish that family and friends go through after losing a loved one.

“It’s hard to explain what it’s like to lose a sister or your daughter,” she said. “The text can wait.”

Her message has been a part of television and radio commercials, billboards, flyers, and pamphlets circulated across the country. She has been traveling from her home in Paxico, Kan., as often as three times a month to high schools and colleges from Colorado to Wisconsin to New York to speak about the dangers of texting while driving.

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“Having a Highway Patrol officer write in a police report that a text message sent at 12:04 p.m. is the reason she’s dead — knowing that you were the person she was talking to at the time she was killed — isn’t something that will ever go away,” Umscheid says in a short documentary that’s part of a national campaign by AT&T.

In 2010, the most recent year for which national numbers are available, more than 3,000 people were killed in distracted-driving accidents, and an estimated 416,000 were injured.

Kansas reported 495 wrecks involving cell phones in 2011, with three deaths and 234 injuries. In Missouri, from January through October 2011, there were 1,490 accidents involving cell phones, with nine deaths and 673 injuries.

Of course, cell phones are just one of the many distractions that challenge drivers. But one study by the Virginia Tech Transportation Institute found that drivers are 23 times more likely to crash if they are texting.