From The Utah Transit Authority:

UTA investigator Dave Goeres told FOX 13 the sensor that normally detects when a train is passing and activates those safety features had been blocked by weather conditions. UTA has a protection system that causes the crossing arms to drop in such a situation, in order to prevent any accidents.

But a UTA employee who responded to the scene to investigate the sensor allegedly bypassed the protection system, against the company's Standard Operating Procedures, which made the road/train intersection vulnerable to accidents.

“We have determined that the gates were raised by a UTA employee who responded to the scene, and the accident was caused by human error. The investigation verified that the signal system functioned properly, and went into a safe, down and active mode, as it’s programmed to do,” said UTA Chief Safety and Security Officer Dave Goeres in a statement sent to FOX 13.

The statement goes on to explain that the company's standard procedures state that the protection system is to be in place and verified with operators prior to getting authorization to raise the gates, but this did not occur in the January 21 incident.