LEC Train Handling and Performance 2 — Questions and Answers
Question 1: When descending a steep grade, what is the primary purpose of making a minimum reduction before the grade?
- To test brake responsiveness before heavier braking is needed (Correct answer)
- To reduce speed for a speed restriction at the bottom
- To equalize air pressure across all brake cylinders
- To notify the rear crew that a grade is approaching
Correct answer: To test brake responsiveness before heavier braking is needed
A minimum reduction before a descending grade tests brake function and establishes control before additional braking force is required.
Question 2: What effect does increasing train speed have on braking distance on level track?
- Braking distance increases proportionally to speed
- Braking distance increases with the square of speed (Correct answer)
- Braking distance remains constant regardless of speed
- Braking distance decreases due to greater wheel-to-rail friction
Correct answer: Braking distance increases with the square of speed
Braking distance increases with the square of speed because kinetic energy—which must be dissipated—is proportional to velocity squared.
Question 3: During cold weather operations, what is the main concern with slack in a long train during initial movement?
- Couplers may freeze and fail to transmit power
- Rapid slack run-in can cause buff forces that derail cars (Correct answer)
- Air hoses may freeze, causing undesired brake application
- Lubricants become too viscous for smooth coupler action
Correct answer: Rapid slack run-in can cause buff forces that derail cars
In cold weather, frozen or stiff wheel bearings and brakes can cause sudden slack run-in when cars start moving, generating dangerous buff forces.
Question 4: What is the correct action when a locomotive's wheel slides during dynamic braking?
- Apply the independent brake to stop the slide immediately
- Reduce dynamic brake effort to allow wheels to recover traction (Correct answer)
- Increase throttle briefly to spin wheels and clear ice
- Sound the horn to warn of reduced braking capacity
Correct answer: Reduce dynamic brake effort to allow wheels to recover traction
Reducing dynamic brake effort decreases the retarding force, allowing slipping wheels to recover traction before increasing braking again.
Question 5: Which train handling technique best prevents run-in when transitioning from upgrade to level track?
- Making a full service brake application just before the crest
- Allowing the train to coast with brakes released as lead units reach level
- Reducing throttle gradually as lead units approach the crest (Correct answer)
- Applying independent brake on locomotives only at the crest
Correct answer: Reducing throttle gradually as lead units approach the crest
Gradually reducing throttle as lead units approach the crest prevents the train from bunching when rear cars are still being pushed uphill.
Question 6: What is 'stretch braking' and when is it primarily used?
- Applying dynamic brakes while simultaneously using throttle to maintain stretch in the train
- Using brakes to maintain train stretch while descending a grade (Correct answer)
- Increasing brake pipe reduction while moving to test brake travel
- Alternating between service and minimum reduction applications repeatedly
Correct answer: Using brakes to maintain train stretch while descending a grade
Stretch braking uses retarding force to keep train couplers in tension, preventing slack run-in on descending grades.
Question 7: When a locomotive engineer receives an emergency brake application signal while operating at track speed, what is the first action?
- Place throttle to idle and wait for the automatic brakes to stop the train
- Place the automatic brake valve in emergency position immediately (Correct answer)
- Apply full dynamic braking then follow with automatic brake application
- Sound the horn and begin reducing speed while investigating the cause
Correct answer: Place the automatic brake valve in emergency position immediately
An emergency signal requires immediate placement of the automatic brake valve in emergency to achieve maximum stopping force as quickly as possible.
LEC Train Handling and Performance 2
When descending a steep grade, what is the primary purpose of making a minimum reduction before the grade?