The 'L'-ert iPhone app notifies 'L' riders when they are arriving at their destination station. View Full Caption 'L'-ert

ALBANY PARK — Since Alex Zielonko moved to Chicago in August, he's had a couple of bad experiences riding the "L."

"I fell asleep on the train on more than one occasion, and I've missed a few stops," said Zielonko, a 22-year-old living in Albany Park. "I have friends who have done the same."

Already looking to make a career coding, Zielonko created "L"-ert, a free iPhone app designed to make sure that sleepy commuters or those lost in the glow of their mobile devices never miss their "L" stop.

The app's pretty simple, both in design and function. Before travel, a commuter can pick the destination station and tell the app to vibrate, make a sound or both just before the train reaches the station.

Alex Zielonko shows off 'L'-ert, an app that alerts CTA "L" riders when they are arriving at their destination stop. View Full Caption DNAinfo/Tanveer Ali

"I kind of think of it as a Casio keyboard from the '80s mixed with a subway door opening somewhere not in Chicago," Zielonko said of the sound his app makes.

The app, which Zielonko began working on at the start of November, hit iTunes Nov. 29. So far, the feedback's been positive.

"Without 'L'ert, I would have missed my first job interview," a person wrote in an iTunes review. "Emerged (sic) in a deep slumber, my phone vibrated which woke me up and allowed me to exit the train and be at my interview with time to spare. Groovy."

Zielonko, who hails from the St. Louis area, plans to enhance his app with the addition of Metra stations and bus stops, the latter of which he admits will be very complicated.

"I'm just one person," Zielonko said.

For now, his first major development project does exactly what he set out to do: send users alerts so they can avoid mornings like the one when Zielonko went too far south and too far north on the Red Line in the same day.

"Lesson learned," said Zielonko, who uses his app every time he takes the train.