On Friday, six months after the incident, the U.S. Department of Transportation’s Federal Railroad Administration (FRA) released a 1,100-page accident report. According to the report, the train heading from Kansas City, Kansas, to Barstow, California, was pulling 167 cars of various types, was 11,374 feet long, and weighed 15,519 tons (31,038,000 lbs.).

“[The railroad companies are] essentially doubling the size of trains, cutting folks who do the inspection on the trains and doing a lot of unnecessary cuts just to save money,” said N. D. Hannah-Jones, who’s also a certified locomotive engineer with BNSF. “And what they’ve done now is taken us from what we are used to and trained to run, as a 7,000-foot, 6,500-ton train, which is very manageable ... we’re seeing trains in excess of 16,000 feet now running through Arizona.”

In conclusion, the FRA report found that the engineer operating the train didn’t use the brakes properly and the train was more than two times the size they were qualified to operate.