The San Bernardino train disaster (sometimes known as the Duffy Street incident or the 1989 Cajon Pass Runaway), was a combination of two separate but related incidents that occurred in San Bernardino, California, United States: a runaway train derailment on May 12, 1989; and the subsequent failure on May 25, 1989, of the Calnev Pipeline, a petroleum pipeline adjacent to the tracks which was damaged by earth-moving equipment during the crash cleanup.

On May 12, 1989, at 7:36 a.m. a 6-locomotive/69-car Southern Pacific freight train (SP 7551 East, computer symbol 1 MJLBP-11) transporting trona lost control while descending Cajon Pass, derailed on an elevated curve and plowed into a residential area on Duffy Street.

The train reached a speed of about 110 miles per hour (180 km/h) before jumping the tracks on an elevated curve that had a posted speed limit of 35 miles per hour (56 km/h) next to Duffy Street, sending the head-end locomotives and several cars off the high railroad bed and into houses on the street below, completely demolishing them.

It was also determined after the wreck that the engineer operating the helper locomotives knew of the faulty dynamic brakes on one of his units, but did not communicate that information to the head end crew.

Engineer Holland remained in his seat at the control stand in unit SP 8278 at the head of the train, and suffered several cracked ribs and a punctured lung.

Thirteen days after the train wreck on May 25, 1989, at 8:05 a.m., shortly after eyewitnesses heard a train pass through the derailment site, the pipeline burst at a point on the curve where the derailment happened, showering the neighborhood with gasoline, which ignited into a large fire that burned for close to seven hours and emitted a plume of flames three hundred feet into the air.

The plots on the south side of Duffy Street closest to the rail line were rezoned as open space by the city so they would not be rebuilt.

It was finally retired on March 17, 2000 and sold to National Railway Equipment Company, who rebuilt it with 5′6″ gauge trucks for MRS Logística (in Brazil) #5313-1.

The buyer had purchased 6,900 tons of trona; thus the mining company, Lake Minerals, contracted for 69 100-ton coal hopper cars (which had a combination of D&RGW and SP reporting marks), which were to be loaded by an outside contractor at Rosamond.

At 9:00 p.m. on May 11, a three-man crew consisting of Frank Holland, an engineer; Everett Crown, a conductor; and Allan Riess, a brakeman, were brought on duty at SP's Bakersfield yard.

The crew was then instructed to take unit SP 8278 (an EMD SD40T-2 "Tunnel Motor") from another consist and add it to theirs, ahead of the dead 7551.

The crew departed Mojave at 12:15 a.m. on May 12, and headed south (railroad direction east) approximately three miles to Fleta, where they were to pick up the 69 freight cars.

Due to maintenance equipment being parked on the track at the south end of the Fleta siding, it was necessary for the train crew to pick up the cars from the north end, take them back to Mojave and run around them, before heading south to Palmdale, where it was originally intended to pick up an additional helper that would be placed on the rear of the train to aid in braking after cresting Cajon Pass.

The dispatcher determined that they would need the dynamic brakes of 5.23 functional engines (6 total) to maintain this optimal speed between 25 and 30 miles per hour (40 and 48 km/h), so picking up only the one additional helper locomotive at Palmdale, as originally planned, would not provide sufficient dynamic braking effort for the 2.2% grade on the west side of Cajon Pass where the derailment happened, so instead of adding the single unit at Palmdale, the dispatcher ordered a two-unit helper set dispatched from the helper pool in West Colton, California.

Consequently, at 1:30 a.m. on May 12, a crew consisting of Lawrence Hill, an engineer, and Robert Waterbury, a brakeman (acting in a position known as a "lookout") was brought on duty at West Colton and transported by company van to Dike (located at Devore), where they boarded a two-unit helper locomotive consisting of units SP #7443 (an EMD SD45R) and SP 8317 (another EMD SD40T-2 Tunnel Motor).

Their instructions were to first help a northbound train (timetable westward) up the hill to Oban, then bring MJLBP-11 back down Cajon Pass to West Colton.

Unit SP 8317 (of the two-unit helper engine set coupled to the rear of the train) also did not have an operative dynamic brake.

The report stated that the derailment was inevitable due to the number of unfortunate circumstances that happened during the trip.

During cleanup, Calnev only inspected short segments of the pipeline – generally around places where train wreckage had landed on top of the pipe.

They did not carry out an excavation of the pipeline through the entire length of the derailment site for a further inspection, or, a hydrostatic test, either of which, if done, would have found the damage and prevented the rupture.

Additionally, the stop-and-check valves downstream from the rupture failed to close, allowing product to flow back down the pipe through Cajon Pass, which strengthened the intensity and duration of the fire.

The disaster was featured in "Runaway Train", a Season 3 (2005) Crash Scene Investigation episode of the Canadian TV series Mayday.

[9] For broadcasters that do not use the series name Mayday, this is one of three Season 3 episodes labeled as Crash Scene Investigation spin-offs, examining marine or rail disasters.