DPU Failure Led to Union Pacific Derailment in Austin

A distributed power unit failure and excessive slack action led to the April 23 Union Pacific derailment in downtown Austin, according to newly published Federal Railroad Administration data.

DPU failure preceded the derailment

The FRA equipment-accident record⁠ identifies the train as northbound ZSAYC-23 on Union Pacific’s Austin Subdivision. It was moving at an estimated 15 mph at milepost 179.66 when three railcars derailed on the main track.

Distributed power unit UP 7331 had failed because of a ground-relay fault. Operations control cleared the train to continue at 45 mph, but it was travelling at 15 mph while descending Austin Hill and approaching a curve with the same 15-mph limit.

According to the accident narrative, slack ran in through the consist after the DPU failure, causing the cars to derail toward the high side of the curve. The FRA assigned primary cause code H504: excessive buffing or slack action associated with train makeup.

A distributed power unit is a locomotive positioned within the train and controlled remotely from the head end. The consist had three head-end locomotives and one remotely controlled midtrain locomotive.

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FRA data records three derailed cars and $1 million damage

The FRA filing lists 239 railcars: 221 loaded and 18 empty. Two loaded cars and one empty car derailed. These figures differ from the initial city response count of seven derailed cars from a 230-car train.

Reported equipment damage reached $484,461, while track damage was estimated at $529,816. The combined cost was $1,014,277.

Although the consist included 12 cars carrying hazardous materials, the FRA recorded no damaged or releasing hazmat cars and no evacuation. No railroad employees or members of the public were injured or killed.

Austin added Union Pacific to emergency planning

The City of Austin’s public-safety briefing⁠ states that cleanup was completed by 4 a.m. on April 24, allowing trains to resume moving over the line.

Union Pacific subsequently met Austin officials on May 13. Railroad contacts and training materials were shared with local public-safety agencies, while Austin Emergency Management planned to incorporate Union Pacific into its training and exercise programme.