On the CTA's 1,200 rail cars, riders are often met with a variety of frightening encounters- from armed robbers and cell phone thieves to fist fights and shoving.
Sometimes, shots are fired and people end up wounded or dead.
"I actually saw some girl pass out from huffing spray paint. It was kind of scary," said Anne Rush, CTA Red Line rider.
Transit officials say a fraction of one percent of all rides on the CTA end in crime. But the I-Team dug deep into raw police data for the actual number of crimes on the CTA in 2012.
The figures are as follows:
-There were more than 6,800 assaults, robberies, thefts and similar offenses.
-According to the statistics, you are twice as likely to become a victim on a CTA train or platform than on a bus or at bus stop.
-On average, 19 CTA passengers are victimized every day.
Police say the fastest growing crime threat across Chicago's transit lines are cell phone thefts- and some commuters agree.
"I was sitting on the train, reading the newspaper and I had it sitting on my lap, then I picked it up for a text message, and a young guy was standing by the door, and when the door opened for his stop, he just snatched it out of my lap and started running," said Tony Taylor, Red Line rider.
The CTA has responded with more than 1,500 surveillance cameras, monitored in a command center.
Transit officials also have approved a $30 million contract to rehire 50 off-duty Chicago police officers for patrol shifts on subway and bus routes.
"We also use what we call civilian dressed officers who are actually riding as passengers. So, we embed them in the system and they ride as passengers, they're fully prepared to react as police officers...I'm really confident that the CTA and the transit system will become increasingly safer," said Cmdr. Nancy Lipman, Chicago Police Department Transportation Section.
According to figures obtained by the I-Team, some locations are more dangerous than others, including:
-The Red Line at Garfield and the Dan Ryan on the South Side. This is the city's third most dangerous CTA center and the scene of 200 reported crimes last year.
-The Green Line at Pulaski and Lake on the West Side. This is the site of more than 300 reported crimes in 2012.
-The Red Line stop at Chicago and State Street. This is the most dangerous CTA location according to the raw numbers, with 359 crimes reported.
With passengers victimized every day, thousands have started fighting back on social media. For more than a year, People of the CTA has been posting videos and photos of bizarre scenes on the public transportation, including pictures of employees who appear to be asleep on the job. It has a following of nearly 100,000 users.
YouTube is also full of passenger cell-phone videos of violent incidents and outrageous images seen on the CTA.
Kevin O'Neil, known on the internet as the CTA Tattler, has blogged about mass transit for nine years.
"Personally I have not seen a big presence of uniformed police officers. Occasionally I will see them. I'm not saying they're never there. I think there's more undercovers working? I won't say that people feel safer," said O'Neil.
The I-Team also noticed a lack of uniformed officers on the CTA on several evenings, while riding different el lines, our producer and crew said they saw no police during six-hour periods.
The public transit unit has 130 officers. Their commander says there is a stronger uniform presence during rush hours, more tactical and plainclothes during the day and overnight.