The National Transportation Safety Board has determined that a combination of three factors was the probable cause of a November 2023 collision between a Chicago Transit Authority train and a snow removal machine.
An aggressive speed reduction command caused a wheel slide, degrading the train’s braking performance. Additionally, the CTA’s decision to disable the automatic track brake application feature of the train’s wheel slide protection system delayed the application of the track brake and further reduced the train’s braking performance.
The federal agency also said that organic material on the rails caused slippery conditions that worsened the wheel slide and degraded the train’s braking performance.
The train had one operator and carried 30 passengers. Six CTA employees were on board the snow removal machine.
Sixteen people were transported to a hospital, treated and released. Three people were critically injured, including the operator.
The train remained upright following the collision, and CTA estimated damages to equipment to be about $8.7 million.
