The National Transportation Safety Board released preliminary findings Tuesday, detailing the moments that led to a harrowing crash involving a Chicago Transit Authority Yellow Line train last month, which left dozens of people injured.
The report details some of the first insights behind the November crash, which involved a CTA Yellow Line and snow removal equipment and ultimately left 38 people wounded, but does not reveal an exact cause of the crash, though an investigation remains ongoing.
According to the findings, the southbound Yellow Line passenger train collided with the snow removal machine around 10:30 a.m. on Nov. 16.
At the time of the crash, the sun was out, conditions were clear and there was no precipitation, the report said.
The track the train was operating one was considered a "double main track" and the location of the accident has a signal system that operates with a stopping distance of 1,780 feet or less. The maximum allowed train speed was 55 mph at the time.
"The passenger train was on a scheduled trip from Dempster Skokie Station to Howard Station. The operator was aware that the snow removal machine was operating on the Yellow Line as part of a training exercise but did not know its exact location," the report states. "Shortly before the collision, the southbound snow removal machine stopped about 370 feet north of a red signal indication. The passenger train was traveling southbound about 54 mph when the operator received a stop command from the signal system because of the snow removal machine stopped on the track about 2,150 feet ahead. The operator immediately initiated a full service braking application to stop the train. The operator then saw the snow removal machine and initiated an emergency braking application. The train decelerated to about 27 mph before striking the snow removal machine."
According to the NTSB, the brake system on the train was designed to slow trains at about 4.1 feet per second squared under such conditions.
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The report noted that investigators took samples of "organic material from the top surface of the rails at the accident site" and said future investigation activity will focus on "the design and configuration of the CTA signal system, the design and braking performance of the railcars involved in the accident, and examination of organic material present on top of the running rails investigators collected to determine what impact, if any, this material had on the accident."
The organic material has been in question since the investigation began, along with a "design problem" with the train's braking system.
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According to preliminary data obtained from the event recorder, the train was traveling at 26.9 miles per hour when it stuck the snow equipment.
"We know that CTA's system saw the snow equipment ahead," Jennifer Homendy, chair of NTSB said last month. "It was supposed to be there. They knew it was going to be there. We also know from our calculations this train on this day was designed to stop within 1,780 feet... it didn't. So now we needed to determine why."
Preliminary findings suggested debris was present at the time and the train wasn't able to stop in time due to the agency's braking system.
"A brand new system today with the same track, they should have had 2,745 feet to stop that train... 2,745 not 1,780 feet," according to the NTSB chair. "That is a design problem."
The stopping distance may be different nowadays due to a variety of factors, including heavier train cars and a greater number of passengers. At the time of the collision, thick and black residue was present on the tracks, Homendy said, adding that the train's wheels were slipping when the operator was braking.
"Preliminary review of the train’s event recorder showed that the wheel slide protection system activated throughout both braking applications," the Tuesday report stated.
Federal investigators said the CTA compiled data that showed since Nov. 1, a similar scenario, in which something was stopped in the next section of track and a train was approaching, occurred 50 times.
As of Tuesday, the CTA said Yellow Line service remains suspended.
"In keeping with NTSB protocol, all inquiries about the incident are being directed to that agency. As such, the CTA is currently unable to discuss the specifics of the ongoing investigation," the agency said in a statement.
