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Uncontrolled Movement, Collision, and Passenger Fatality on the Angels Flight Railway in Los Angeles, California February 1, 2001

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Railroad Accident Report

NTSB/RAR-03/03

PB2003-916303

Notation 7575

National Transportation Safety Board Washington, D.C.

References

Factual Information

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Railroad Accident Report

were on board either car during movement. The single operator in the upper station house was responsible for visually determining that the track and vehicles were clear for movement, closing the platform gates, pressing the start button,$^{3}$ monitoring the operation of the funicular cars, observing car stops at both stations, and collecting fares from passengers.

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Figure 1. Angels Flight viewed from upper station.

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Figure 2. Angels Flight car at the passing siding with upper station in the background.

Factual Information

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Railroad Accident Report

Accident Narrative

Just after noon on February 1, 2001, the Angels Flight operator was making change for a customer when he saw the ascending car stop about 30 feet from the top platform. As he focused his attention on the stopped car, he said, it slid downward a few feet, hesitated for an instant, and then began accelerating downward. The operator said that he had seen cars stop on the hill before but had never seen a car reverse direction. He said that as soon as the ascending car started moving downward, he pushed the emergency stop button. He said that the car did not slow or stop after he pushed the button and that the car continued gaining speed until it collided with the other car near the bottom of the hill. (See figure 3.) Persons waiting at the bottom platform who witnessed the collision said that the struck car stopped before the collision.

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Figure 3. Position of cars after collision.

The runaway car derailed during the crash; the struck car did not. The derailment marks and the dispersal of debris after the collision indicated that both cars moved about 20 feet downward from the point of impact.

Emergency Response

The collision occurred about 12:17 p.m. in a busy section of downtown Los Angeles. Local emergency response agencies reported receiving multiple phone calls almost immediately. A Los Angeles police officer heard the collision and responded to the accident scene within 1 minute. The first fire department vehicle arrived within 4 minutes. Firefighters and paramedics used wooden extension ladders to reach, provide emergency

Factual Information

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Railroad Accident Report

treatment to, and evacuate the passengers. (See figure 4.) The injured passengers were strapped to backboards that were lowered to the ground by firefighters standing along the lengths of the ladders. (See figure 5.)

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Figure 4. Ladders placed for the emergency evacuation. Walkway on the other side of the tracks can be seen below track level.

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Figure 5. Passenger evacuation after collision.

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Railroad Accident Report

Injuries

At the time of the accident, 8 people were aboard the runaway car and 12 were aboard the car that was struck. One passenger was ejected from the open end of the struck car. Other passengers were injured when they struck vertical grabrails, each other, and various objects inside the cars. One of these injured passengers, an 83-year-old man, died later at a hospital. The Los Angeles County coroner's office reported the cause of his death as multiple traumatic injuries. Debris from the collision fell onto the surrounding area and injured one pedestrian.

Table 1. Injuries.$^{a}$

Damage

The lower inboard quarter of the runaway car struck the upper inboard quarter of the stationary car. Approximately 4 feet of each car was crumpled. (See figures 6 and 7.)

Factual Information

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Railroad Accident Report

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Figure 6. View of some of the exterior damage to cars.

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Figure 7. View of some of the interior damage to one of the cars.

Factual Information

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Railroad Accident Report

The concrete crossties and rail fasteners under the derailed car were scored and dislocated. Some internal haul system components were broken and destroyed. Monetary damage estimates provided by the Angels Flight Operating Company were as follows:

Table 2. Damage.

Meteorological Information

At the time of the accident, the temperature was 72° F, winds were calm, and the skies were clear.

Postaccident Onsite Examination

The system's operating machinery was in the machinery room underneath the operator's station house. The Angels Flight haul system consisted of a separate cable, drum, axle, and planetary gear for each car, with a sun gear driven by a single 100-horsepower electric motor. (See figure 8.) The driven sun gear meshed with the planetary gear for the Olivet car (the struck car in this accident), which in turn meshed with the planetary gear for the Sinai car (the striking car). Axle shafts (about 3 inches in diameter) connected the planetary gears with their respective cable drums. This gear arrangement meant that the two planetary gears, and thus the two cable drums, were counter-rotational, resulting in counterbalancing loads as one car descended while the other ascended.

Emergency brakes (discussed in detail later in this report) that were designed to stop the rotation of the drum were found to be in the released position even though the emergency stop button had been pressed by the operator. Initial inspection also revealed that the 7/8-inch-diameter cable for the Sinai car was intact but that two rows of the wound cable had de-spooled from its drum.

Reconstruction of Angels Flight

The City of Los Angeles Community Redevelopment Agency (Community Redevelopment Agency) purchased Angels Flight in 1962 because Angels Flight was within the Bunker Hill district urban renewal project area. At that time, Angels Flight was

Factual Information

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Railroad Accident Report

〔图〕Axle ShaftToOlivetGearboxCarOlivet Cable DrumPoint of FailureSinai Cable DrumToSinaiCarServiceMotorBrakeAxle ShaftLEGEND

Figure 8. Schematic of Angels Flight haul system.

a designated historic and cultural monument. In response to community interest in and concern about the eventual fate of Angels Flight, the Community Redevelopment Agency pledged to restore the funicular railway as part of the Bunker Hill urban renewal project.

In 1991, the Community Redevelopment Agency hired Parsons Brinckerhoff Quade & Douglas Engineering (Parsons) as an advisor on the reconstruction of Angels Flight. In 1992, the Community Redevelopment Agency hired Harris and Associates (Harris) as the construction manager for the renovation of Angels Flight. In 1993, Harris hired Parsons to design specifications for the project.

On June 17, 1993, the Community Redevelopment Agency approved the Angels Flight Restoration and Reconstruction Plan. The Community Redevelopment Agency selected Pueblo Contracting Services, Inc., (Pueblo) to be the general contractor for the Angels Flight reconstruction. On November 17, 1994, the Community Redevelopment Agency awarded two construction contracts to Pueblo to rebuild Angels Flight according to the Parsons specifications, and construction began soon afterward. In 1995, Pueblo hired Lift Engineering (Yantrak $^{4}$) to implement Parsons's conceptual design by designing and building the funicular drive, control, and braking systems and the haul and drum assembly. (See figure 9.) About 15 months later, a ceremonial opening of Angels Flight took place on February 23 through 25, 1996.

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Railroad Accident Report

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Figure 9. Organizations involved in Angels Flight design, construction, and operation.

During the project, the Community Redevelopment Agency had responsibility for contract negotiations, safety oversight, deletions from and modifications of the original safety designs, and safety certification. As owner of the funicular, the Community Redevelopment Agency made final decisions concerning the original engineering design of Angels Flight and subsequent modifications. The project lasted from 1991 through April 1997, when the completed funicular was leased to the nonprofit Angels Flight Railway Foundation, which entered into a 99-year lease with the Community Redevelopment Agency to operate and maintain Angels Flight. The Community Redevelopment Agency maintained ownership but was not involved with the operation or maintenance of Angels Flight. The Angels Flight nonprofit foundation contracted with the for-profit Angels Flight Operating Company to manage the operation and maintenance of the railway.

The Angels Flight Operating Company hired the Millar Elevator Service Company (Millar) in 1996 to perform maintenance and inspections. The Millar elevator mechanic assigned to Angels Flight eventually became the maintenance contractor, and he subsequently became vice president of the Angels Flight Operating Company while simultaneously remaining an employee of Millar.

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Railroad Accident Report

Angels Flight Design

Parsons's specifications for the funicular system included a trackway design with standard steel rails attached to concrete ties, all supported on an elevated framework from 10 to 20 feet above the ground. (See figure 10.)

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Figure 10. Elevation of Angels Flight track (at left).

Drive System

When originally built in 1901, Angels Flight was a basic funicular, with two cars, connected by a single cable, whose weights counterbalanced each other. The haul system was powered through an arrangement of wheels and gears that the cable passed around at the top of the hill.

For the reconstruction of Angels Flight, Parsons did a conceptual design of the haul system. (Subsequently, Yantrak modified the haul system design. A schematic diagram of the Yantrak haul system is shown in figure 8.) Instead of a single cable connecting the two cars, the new haul system consisted of an autonomous cable, drum, axle, and planetary gear for each car, with a common driven, or sun, gear. Thus, each car was attached to its own cable; each cable was wound around and attached to the outside of an independent 6-foot-diameter drum; each drum was connected to its own axle; the axles were connected inboard to separate planetary gears; and the planetary gears were meshed together. One of the planetary gears meshed with a driven sun gear that was powered by a 100-horsepower motor. This design made Angels Flight a double winding drum system that was operated as a double reversible funicular.$^{5}$ Maximum operating speed was about 352 feet per minute (4 miles per hour).

Factual Information

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Figure 11. Deropement device.

Angels Flight had been in passenger service for several months before the deropement switches were added. On August 12, 1996, Harris sent a letter to Pueblo listing “de-roping annunciation and system halting” as requirements that had not been completed. The deropement switches described above were subsequently added.

Operations

Gearbox Overheating

According to the Angels Flight president, high oil temperatures in the gearbox became a concern soon after Angels Flight opened in February 1996. Angels Flight representatives made repeated telephone calls to Yantrak in a continuing attempt to evaluate and correct the problem. Yantrak's initial response referenced a memorandum from Fairfield Manufacturing,$^{8}$ which stated:

... oil temperatures up to 225 degrees F will not cause gear or seal problems in your Angels Flight drive. ... The level of oil in the box will change your operating temperature. I would lower it to the centerline and see how much that helps. As you continue to lower the level, the temperature will fall to a point where you are no longer getting enough lubrication and then it will start to rise. Since your unit is critical, I would not take this test to the point where you get the temperature rise

Factual Information

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Railroad Accident Report

splined receiving hubs for the planetary gears and the cable drums. The splines were designed to lock these components in place.

The Angels Flight gearbox was disassembled. The gears, shafts, and splines from both the Sinai side and the Olivet side were removed and examined and the results documented. Parties to the investigation were present.

Axle Shafts and Splines. The Caterpillar-manufactured axle shafts for both the Sinai and the Olivet sides were found to be in good condition. For the Sinai car, metal shavings were found on the surface of the axle shaft, and the splines of the end of the axle shaft that engaged the planetary gear were slightly worn but otherwise intact. (See figure 12.) The outside diameter of the Sinai shaft, measured at the splines that mated with the receiving hub splines, was 2.912 inches. The outside diameter for the Olivet shaft at the corresponding splines was 2.917 inches.

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Figure 12. Splined end of Sinai axle shaft that engaged the planetary gear receiving hub.

Both axle shafts were subjected to Rockwell C hardness tests.$^{13}$ The average Rockwell C hardness for the Olivet shaft was 57 and for the Sinai shaft, 60. These hardness levels are near the higher end of the range measured for steel and indicate that the axle shafts were subjected to a hardening heat treatment to maximize their load-bearing capacity.

Factual Information

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Railroad Accident Report

Sinai Receiving Hub and Splines. The Yantrak-supplied receiving hub for the Sinai planetary gear was pressed out of the gear and then sectioned by electron discharge machining. The splines that mated with those of the axle shaft were found to be stripped, thereby preventing the interlocking of the planetary gear with the cable drum. (See figure 13.) Thus, the Sinai car's cable drum had effectively become disconnected from the drive mechanism, and it became freewheeling. The metal shavings removed from the surface of the Sinai shaft were consistent with the metal of the sheared female splines of the planetary gear receiving hub with which the Sinai axle shaft splines mated. The sectioned piece from this receiving hub was polished using standard metallurgical techniques and then examined under an optical microscope. The microstructure was found to consist of ferrite and pearlite typical of an unhardened steel. The sample of the receiving hub was then subjected to hardness testing at a variety of locations through its cross section, both near and away from the spline teeth. The hardness of the steel was between 78.0 and 80.5 on the Rockwell B scale for softer metals and was consistent throughout the piece. The receiving hub's average Rockwell B hardness of 79 is typical of a nonheat-treated, soft steel. Thus, the Sinai receiving hub was softer than the axle shaft.

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Figure 13. Section of planetary gear receiving hub showing stripped splines.

Ball Bearings. The ball bearings supporting the receiving hubs on both the Sinai side and the Olivet side of the gearbox were inspected. The bearings on both the Sinai and Olivet sides were coated with a hard black material where they were exposed to the oil reservoir. The bearing races, or grooves for the ball bearings, showed some bluing.

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Analysis

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Railroad Accident Report

Brake System Failure

Once the cable drum for the Sinai car became disconnected from the drive gear system, the car's haul cable was able to unwind freely as gravity pulled the car down the incline. The emergency braking system was designed to prevent such an occurrence by clamping against the cable drum flanges to stop the drum's rotation. Had the emergency brakes functioned when activated by the operator, the descent of the car would have been stopped even though the cable drum was no longer connected to the rest of the drive system. The Safety Board therefore concludes that had the Angels Flight emergency braking system been functional on the day of the accident, the brakes would likely have stopped the descent of the runaway car and prevented the collision.

The investigation determined that if the Angels Flight service and emergency braking systems had been installed in accordance with the design drawings and parts list, neither of the brakes would have released, and Angels Flight could not have been operated. In this design, normally open solenoid valves would have been required to apply and release the brakes in a conventional, fail-safe manner. At some point, either during initial brake system installation and testing or shortly thereafter, at least the service brake system had to have been equipped with a normally open valve. Postaccident inspection found that the service brake was still equipped with a normally open valve, and it operated properly. But the emergency brake system was equipped with a normally closed valve. Because the valve had failed in the normally closed position, the emergency brake could be released, but it could not be reapplied when needed.

Angels Flight records indicated that a solenoid valve had burned out and been replaced with a normally closed valve as indicated on the drawings and parts list. But as noted, this would not have allowed the system to be operated. Although it cannot be known for sure, it is possible that the new valve was inoperative when it was installed or was defective and failed very quickly after its initial activation. Either scenario would explain how the system was able to be operated and would account for the valve configuration found during the postaccident inspection.

Although the test procedure for the Angels Flight emergency brakes was conducted daily, the button that activated those brakes simultaneously activated the service brake. Therefore, this method of testing could not confirm that both braking systems were operational. The Safety Board therefore concludes that the brake system as designed was inoperable, as implemented was not fail-safe, and was further inadequate because the emergency brakes could not be activated independent of the service brake and tested separately, which would have revealed that the system's emergency brakes were inoperative.

The Safety Board believes that before recommencing passenger service on the Angels Flight funicular railway, the Community Redevelopment Agency should require that the current Angels Flight emergency braking system (acting on the cable drums) be redesigned to allow it to be tested independent of other braking systems.

Conclusions

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Probable Cause

The National Transportation Safety Board determines that the probable cause of this accident was the Yantrak Company's (Lift Engineering's) improper design and construction of the Angels Flight funicular drive and the failure of the City of Los Angeles Community Redevelopment Agency, its contractors (Pueblo Contracting Services, Yantrak, and Harris and Associates), and the California Public Utilities Commission to ensure that the railway system conformed to initial safety design specifications and known funicular safety standards.

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Recommendations

As a result of its investigation, the National Transportation Safety Board makes the following safety recommendations:

To the California Public Utilities Commission:

Adopt comprehensive funicular design, construction, and operation regulations that include provisions for (1) emergency stopping under all foreseeable failure modes, (2) containment of passengers in the event of a collision, and (3) emergency egress and ingress for passengers and emergency responders. (R-03-14)

Before certifying Angels Flight to restart passenger service, independently verify that the drive system meets accepted industry standards and engineering practices and that the funicular includes provisions for (1) emergency stopping under all foreseeable failure modes, including track brakes or some other independent backup system on the cars to prevent a runaway car if a failure occurs in the cable or its associated braking systems; (2) containment of passengers in the event of a collision; and (3) emergency egress and ingress for passengers and emergency responders. (R-03-15)

To the City of Los Angeles Community Redevelopment Agency:

Before recommencing passenger service on the Angels Flight funicular railway:

Conduct a comprehensive review of the design and specifications for the Angels Flight drive system, then make the design or component changes necessary to ensure that the drive system meets accepted industry standards and engineering practices. (R-03-16)

Require that the current Angels Flight emergency braking system (acting on the cable drums) be redesigned to allow it to be tested independent of other braking systems. (R-03-17)

Require that the organization(s) responsible for operating and maintaining the Angels Flight funicular develop and follow detailed operating, inspection, and maintenance procedures to ensure the operational integrity of the system and safety of passengers. (R-03-18).