On September 25, 2013, at 4:17 a.m. central daylight time, BNSF Railway (BNSF) eastbound train BLACWSP223A (7891 East) struck the rear end of standing BNSF train SLHTLPC223A (6746 East) on main track no. 2 near Amarillo, Texas. Several cars from 7891 East derailed and fell across the adjacent track, main track no. 1. Approaching BNSF westbound train ZWSPSBD724L (6943 West) struck the derailed cars.
The engineer and the conductor of train 7891 East recalled passing signals warning them of the train ahead. However, the signal at milepost 543.65 was not lit because the bulb had burned out (also known as a dark or improperly displayed signal). Had the bulb not been burned out, the signal would have displayed a red aspect, which would have required them to stop the train before proceeding at restricted speed. When they passed this signal, neither crewmember noticed that the signal was dark. A dark signal also required the crew to stop the train before proceeding at restricted speed.
The engineer stated that he thought the dim (low-beam) headlight from the rear end locomotive helper unit of 6746 East was an approaching train on the adjacent track. The conductor thought the headlight had a yellow cast to it and was a wayside signal. Neither crewmember thought the headlight was on the rear of a standing train.
Five of the six involved train crewmembers received injuries and were hospitalized. The weather was clear with 10-mile visibility, and the temperature was 59°F. Estimated damage was $4.4 million.