Train Driver Braking Systems and Train Dynamics 1 — Questions and Answers
Question 1: What is the primary braking system used on freight trains in the United States?
- Hydraulic disc brakes
- Pneumatic air brakes (Correct answer)
- Magnetic track brakes
- Regenerative electric brakes
Correct answer: Pneumatic air brakes
Pneumatic air brakes, standardized by George Westinghouse, use compressed air to actuate brake cylinders and are the standard system for US freight trains.
Question 2: What happens when brake pipe pressure drops to zero on a train equipped with standard air brakes?
- Brakes release completely
- Brakes partially apply and hold
- Emergency brakes apply automatically throughout the train (Correct answer)
- The system resets and waits for operator input
Correct answer: Emergency brakes apply automatically throughout the train
A complete loss of brake pipe pressure triggers an emergency brake application because the system is fail-safe — brakes apply when air pressure is lost.
Question 3: What is 'dynamic braking' on a diesel-electric locomotive?
- Using traction motors as generators to create braking resistance (Correct answer)
- Applying brakes rapidly during high-speed operations
- A system that automatically adjusts brake pressure based on speed
- Emergency braking using a secondary hydraulic system
Correct answer: Using traction motors as generators to create braking resistance
Dynamic braking converts traction motors into generators, dissipating kinetic energy as heat through resistor grids to slow the train without using friction brakes.
Question 4: What is the standard charged brake pipe pressure for freight trains in the United States?
- 70 psi
- 80 psi
- 90 psi (Correct answer)
- 110 psi
Correct answer: 90 psi
The standard brake pipe pressure for US freight trains is 90 psi when fully charged and brakes are released; passenger trains typically use 110 psi.
Question 5: What is a 'penalty brake application'?
- A fine assessed to operators who apply brakes incorrectly
- An automatic emergency brake activation triggered by a safety system (Correct answer)
- A reduced-pressure application used in yard operations
- The gradual pressure reduction used when stopping at a station
Correct answer: An automatic emergency brake activation triggered by a safety system
A penalty brake application is an automatic emergency brake activation triggered by safety systems such as PTC, cab signal alerters, or overspeed detection.
Question 6: What does 'independent braking' control on a locomotive?
- Only the locomotive's brakes, without affecting the rest of the train (Correct answer)
- The brakes on trailing locomotive units only
- A backup system separate from the main air brake circuit
- Brakes on a single axle for precision stopping
Correct answer: Only the locomotive's brakes, without affecting the rest of the train
The independent brake applies or releases only the locomotive's brakes without changing brake pipe pressure or affecting brake application on any of the train's cars.
Question 7: What does the automatic brake handle in a locomotive cab primarily control?
- Dynamic braking engagement level
- Independent locomotive brake cylinder pressure
- Brake pipe pressure for the entire train (Correct answer)
- Parking brake release mechanism
Correct answer: Brake pipe pressure for the entire train
The automatic brake handle regulates brake pipe pressure, which causes brakes to apply or release throughout the entire train automatically.
Train Driver Braking Systems and Train Dynamics 1
What is the primary braking system used on freight trains in the United States?