Site of collision.

​Site of the collision. (Courtesy of the city of Pecos.)​

Union Pacific Railroad Train Collision with Combination Vehicle

What Happened

T​his information is preliminary and subject to change.

​On December 18, 2024, about 5:00 p.m. local time, westbound Union Pacific Railroad (UP) train ZAILA-18 derailed after colliding with a northbound highway vehicle that was traversing the Cedar Street (or US Route 285) highway-railroad grade crossing in Pecos, Texas. Train ZAILA-18 struck a 2015 Peterbilt truck-tractor in combination with a 2016 Scheuerle hydraulic platform semitrailer (a combination vehicle) operated by Boss Heavy Haul LLC and transporting an oversize load. As a result of the collision, the 4 head-end locomotives and the first 11 railcars derailed, and the derailed locomotives released about 9,000 gallons of locomotive diesel fuel into the ground. The collision displaced the combination vehicle’s load, which struck a municipal building. The engineer and the conductor of train ZAILA-18 were fatally injured; three bystanders were transported to a local hospital, treated for minor injuries, and released. UP estimated damages to signals, equipment, and track to be about $4 million; Boss Heavy Haul LLC estimated damages to the combination vehicle and the load to be about $2.2 million.[1] At the time of the accident, visibility was clear; the weather was 55°F with no precipitation.

​Train ZAILA-18, crewed by an engineer and a conductor, was traveling from Shreveport, Louisiana, to Los Angeles, California. The train consisted of 4 locomotives and 47 intermodal railcars.[2] The consist included seven intermodal shipping containers carrying hazardous materials.[3] These containers did not breach or release hazardous materials. ​​

The combination vehicle was traveling from Houston, Texas, to Mentone, Texas.[4] A single driver operated the combination vehicle, which was escorted by two pilot vehicles and a uniformed police motorcycle escort. The load, a demethanizer tower, was 12 feet wide, 116 feet long, and 91,000 pounds.[5]

The combination vehicle entered the highway-railroad grade crossing about 1 minute before the collision. The grade crossing was equipped with flashing lights, crossbucks, gates, and bells. The grade crossing’s warning equipment activated and signaled the train’s approach while the combination vehicle was blocking the railroad tracks. Preliminary review of event recorder data from the third locomotive showed that the train ZAILA-18 crew initiated an emergency braking application shortly before the collision, and the train slowed from about 68 mph to about 64 mph before striking the truck. [6] The maximum authorized speed in the area for railroad traffic was 70 mph.[7]

While on scene, National Transportation Safety Board investigators reviewed radio logs; conducted interviews; reviewed surveillance camera video; made sight-distance observations; examined the track, signals, locomotives, and railcars; examined the highway-railroad grade crossing and the combination vehicle; reviewed Boss Heavy Haul LLC’s policies, procedures, and training programs; and recovered data from the lead locomotive’s event recorder and external- and internal facing image recorders for further review.

The National Transportation Safety Board’s investigation is ongoing. Future investigative activity will focus on site modeling, accident data analysis, highway-railroad grade crossing safety, locomotive cab survivability and crashworthiness, and carrier requirements for traversing grade crossings while transporting oversize loads.

Parties to the investigation include the Federal Motor Carrier Safety Administration; the Federal Railroad Administration; the Texas Department of Transportation; the city of Pecos; UP; Boss Heavy Haul LLC; the Brotherhood of Locomotive Engineers and Trainmen; and the International Association of Sheet Metal, Air, Rail and Transportation Workers.


​ [1] At the time of this report, the city of Pecos had not finalized its estimated damages.

 [2] An intermodal railcar is designed to carry intermodal shipping containers used in intermodal freight transportation. An intermodal railcar often comprises a pack of multiple smaller well railcars, each carrying one or more shipping containers. Each pack is counted as a single railcar in the consist.

​ [3] (a) These intermodal containers were offered for shipment with the following hazardous materials as specified in Title 49 Code of Federal Regulations Part 172: UN3268, safety devices, electrically initiated, a Class 9 miscellaneous hazardous material; UN3481, lithium-ion batteries, contained in equipment, a Class 9 miscellaneous hazardous material; UN1133 adhesives, containing a flammable liquid, a Class 3 flammable liquid; and UN3171, battery-powered vehicle or battery-powered equipment, a Class 9 miscellaneous hazardous material. (b) The derailed equipment included one of these shipping containers.

 [4] The Texas Department of Transportation authorized this origin and destination; the Cedar Street highway-railroad grade crossing was included within the permit-designated route.

 [5] A demethanizer tower is a piece of infrastructure used in the oil and gas industries.

​ [6] An emergency braking application uses the maximum brake force available and is intended to stop the train as quickly as possible.

 [7] Maximum authorized speed was set by UP Toyah Subdivision Sunset Timetable Number 6, effective May 16, 2023.

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