On November 16, 2023, about 10:30 a.m. local time, southbound Chicago Transit Authority (CTA) Yellow Line passenger train (train 593) collided with a stationary CTA snow removal machine (S-500) on south Skokie track 1 near Howard Yard and derailed.[1] The train was carrying 1 operator and 30 passengers; there were 6 CTA employees on board the snow removal machine. Sixteen people were transported to a hospital, treated, and released. Three people were critically injured, including the operator. There were no fatalities. The train remained upright following the collision. CTA estimated damages to equipment to be about $8.7 million. At the time of the accident, visibility conditions were daylight and clear; the weather was 61°F with no precipitation.
[1] (a) All times in this report are local. (b) The snow removal machine (S-500) was purchased by CTA from Mitsubishi International Corporation in 1981. The machine was designed to operate over track. (b) Howard Yard is CTA’s rail yard located north of Howard Station.
We determined that the probable cause of the collision between Chicago Transit Authority (CTA) passenger train 593 and snow removal machine S-500 was a combination of three factors:
- an aggressive speed reduction command that resulted in wheel slide and degraded the train’s braking performance,
- CTA’s decision to disable the automatic track brake application feature of the train’s wheel slide protection system, delaying application of the track brake and further reducing the train’s braking performance, and
- the presence of organic material on the rails that caused slippery conditions that worsened the wheel slide and further degraded the train’s braking performance.
