Impatient passengers led to delays in rush hour subway traffic on Tuesday, causing a slowdown that lasted almost four hour.

The delay began when a packed subway train had to stop for an hour due to a malfunctioning train ahead. The passengers got anxious in the heat and stuffy atmosphere and left the train.

The eight-car train had stalled about 8 a.m. inside a tunnel near Clark.

The evacuation forced officials to cut off power to part of the Blue line, which travels between the West Side and O'Hare International Airport.The step was taken to ensure the safety of the passengers so that no one got hurt by touching the electrified third rail.

Four people had to be hospitalized although their injuries were not serious.

Ron Huberman, president of the Chicago Transit Authority said, "If those particular passengers had not self evacuated, we could have gotten people out on trains and restored service much sooner," reported the New York Times.