The Most Dangerous Escalator in Rome

Key Concepts:

• Escalator safety mechanisms (motor, main brake, auxiliary brake)
• Escalator history (Jesse Reno, George Wheeler, Charles Seeberger, Otis Elevator Company)
• Escalator design (step chain, tracks, comb plate, skirt brush, handrail)
• Regenerative braking in escalators
• Rome escalator accident (2018) - causes and investigation
• Maintenance and safety responsibilities
• Human factors in escalator safety

1. Rome Escalator Accident (October 23, 2018):

• Thousands of football fans were heading to a game in Rome.
• At 7:03 pm, approximately 50 people were on the escalator, quickly doubling in number within 30 seconds.
• The weight of the passengers increased the load on the main motor, which applied a counter torque to slow the descent.
• By 7:04 pm, the crowd had tripled, and the motor reached its limit, causing the drum to slip.
• The escalator's safety relay tripped, cutting power to the motor, and the main brake engaged, but it failed due to insufficient friction (37% of the manufacturer's specification).
• At 7:05 pm, the auxiliary brake, the final safety system, also failed because it had been partially disabled with plastic straps, reducing its stopping power by 50%.
• The stairs plummeted, causing a pileup at the bottom, injuring 24 people.
• The Republica station was closed for several months for technical and criminal investigations.

2. History and Evolution of Escalators:

• 1896: Jesse Reno invented the "Continuous Elevator," a conveyor belt-like device at Coney Island, used as a theme park attraction. It had a 25-degree incline and moved people up seven feet. Over 75,000 people rode it in two weeks.
• People stood still on Reno's invention, prompting the need for a moving staircase.
• Harrods in England installed a similar device, but it was so unsettling that staff offered brandy to men and smelling salts to women.
• Revolving stairs were an early attempt at a moving staircase but had issues with treacherous entry and exit.
• George Wheeler's design, which forms the basis of modern escalators, uses a step chain with wheels that follow separate tracks to keep the steps level.
• Charles Seeberger bought Wheeler's patent and partnered with the Otis Elevator Company.
• 1900: The first commercial escalator was showcased at the Paris Exposition Universelle, drawing large crowds.
• Early escalators had smooth, flat stairs and a dangerous gap at the top, leading to incidents with clothing getting caught.
• A triangular shunt was installed to force riders to exit to the left, but this was awkward.
• Modern escalators use grooved steps that interlock with a comb plate to prevent items from getting stuck.
• Skirt brushes were added in 1982 to address gaps on the sides of the escalator.

3. Modern Escalator Design and Safety Features:

• A typical subway escalator has a 50-kilowatt electric motor.
• A reduction gearbox converts the motor's high-speed, low-torque output to a slower, higher-torque output.
• The motor is connected to a reinforced steel step chain that pulls the stairs around a loop.
• Each step is attached to the chain through a single axle, allowing it to rotate.
• Two sets of wheels on each step follow separate tracks to control the angle of the step.
• The handrail is driven by a separate motor and friction wheel and is calibrated to move 2% faster than the steps to compensate for wear.

4. Regenerative Braking:

• AC induction motors in modern escalators regulate speed effectively.
• On downward escalators, the weight of passengers can drive the motor, causing it to generate electricity through regenerative braking.
• The motor acts as a generator, converting mechanical energy into electrical current, which can be used to power other devices.

5. Rome Escalator Accident Investigation Findings:

• The investigation revealed that the main brake's stopping power was significantly below specifications.
• The auxiliary brake had been deliberately disabled with plastic straps.
• Error codes had been turned off, preventing the recording of critical malfunctions.
• Maintenance records were incomplete, and evidence of major work was missing.
• The investigation pointed to neglect and falsification by those responsible for maintenance.
• Maintenance responsibilities had shifted to a new contractor, Metro Roma, in June 2017.
• Metro Roma and the Transit Authority ATAC were found to have engaged in negligent maintenance and falsified records.
• 11 suspects were named, and three ATAC managers and the chief of Metro Roma were suspended.
• Safety devices had been deliberately sabotaged to avoid shutdowns.
• A wiretap revealed an ATAC manager, Renato Domico, expressing indifference to the possibility of more escalator failures.

6. Escalator Safety and Maintenance:

• When properly maintained, escalators have enormous safety margins.
• Each system is engineered to handle forces far beyond normal service conditions.
• Proper maintenance is critical to ensuring escalator safety.
• The breaking load of a step is greater than 15 kilonewtons (1.5 tons).

7. Human Factors and Responsibility:

• The Rome escalator accident was attributed to human failure rather than engineering defects.
• Humans have a duty of care to maintain systems and ensure the safety of others.
• Jesse Reno's invention of the escalator stemmed from his desire to solve a frustrating, everyday problem.

8. Notable Quotes:

• Philippe Jullian described the escalator at the Paris Exposition as "the jolliest attraction at the exhibition" and noted it caused "many an incident worthy of the vaudeville."
• ATAC Manager Renato Domico: "If you run the numbers, out of 700 escalators, there'd be like three or four more dropping. Come on."

9. Technical Terms:

• Counter Torque: A force that opposes the rotation of an object.
• Safety Relay: An electromechanical switch used to cut power in an emergency.
• Reduction Gearbox: A gear system that reduces speed and increases torque.
• Step Chain: A reinforced steel chain that pulls the stairs around a loop.
• Comb Plate: A grooved plate at the top of the escalator that interlocks with the steps.
• Skirt Brush: A safety feature added to the side of the escalator to prevent objects from getting trapped.
• AC Induction Motor: An electric motor that uses alternating current to create a rotating magnetic field.
• Regenerative Braking: A process where a motor converts mechanical energy into electrical energy during braking.

10. Conclusion:

The video details the history, design, and safety features of escalators, highlighting the importance of proper maintenance and human responsibility. The Rome escalator accident serves as a stark reminder of the consequences of negligence and deliberate sabotage. While escalators are generally safe when properly maintained, human factors play a crucial role in ensuring their continued safety and reliability. The evolution of the escalator, from Reno's initial invention to modern regenerative braking systems, demonstrates continuous innovation aimed at improving safety and efficiency.